ISO/FDIS 11277

• Abstract:

  This document specifies a basic method of determining the particle size distribution applicable to a wide range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with the less common soils mentioned in the introduction. This document has been developed largely for use in the field of environmental science, and its use in geotechnical investigations is something for which professional advice might be required. A major objective of this document is the determination of enough size fractions to enable the construction of a reliable particle-size-distribution curve. This document does not apply to the determination of the particle size distribution of the organic components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It is also realized that the chemical pre-treatments and mechanical handling stages in this document could cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary particles, even though such primary particles could be better described as aggregates. If such disintegration is undesirable, then this document is not used for the determination of the particle size distribution of such weakly cohesive materials.

• Status: Not Published
• ICS: 13.080.20 - Physical properties of soils
• Technical Committee: ISO/TC 190/SC 3 - Chemical and physical characterization
• Drafting Committee: ISO/TC 190/SC 3/WG 14 - Physical methods
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 25-Sep-2026
• Completion Date: 25-Sep-2026
• Ref Project: oSIST ISO/DIS 11277:2025 - Soil quality - Determination of particle size distribution in mineral soil material - Method by sieving and sedimentation

• Revises: ISO 11277:2020/Amd 1:2024 - Soil quality — Determination of particle size distribution in mineral soil material — Method by sieving and sedimentation — Amendment 1
• Effective Date: 07-Jan-2025
• Revises: ISO 11277:2020 - Soil quality — Determination of particle size distribution in mineral soil material — Method by sieving and sedimentation
• Effective Date: 07-Jan-2025

Overview

ISO/FDIS 11277 specifies an internationally recognized method for determining the particle size distribution in mineral soil material. Utilizing a combination of sieving and sedimentation, this standard provides clear procedures applicable to a broad range of mineral soils, including the mineral fraction of organic soils. The core aim is to enable construction of a reliable particle-size-distribution curve, critical for understanding soil quality and behaviour. While primarily developed for environmental science applications, the standard can be referenced for certain geotechnical situations, although expert consultation is recommended for such cases.

Key Topics

• Particle Size Distribution in Mineral Soils
  The standard details protocols for quantifying the range and proportion of particle sizes within a soil sample, expressed by mass. It distinguishes between procedures for coarser materials (above 2 mm) and finer materials (below 2 mm).

• Method by Sieving and Sedimentation

  • Dry sieving is specified for particles larger than 2 mm.
  • Wet sieving and sedimentation applies to material less than 2 mm, using dispersing agents and, when necessary, removing organic matter, soluble salts, and cementing materials.
  • Both pipette and hydrometer sedimentation methods are referenced, with pipette seen as standard.

• Sample Handling and Preparation
  Guidance is included on representative field sampling, required sample sizes, apparatus, and preparation steps based on ISO 11464, ensuring consistency and reliability of results.

• Exclusions and Limitations

  • The standard is not suitable for the particle-size analysis of organic soil components (plant/animal remains).
  • Special note is made of fragile, weakly cohesive materials that may break down during preparation-ISO 11277 may not be appropriate in these cases.

• Reporting and Data Expression
  Results are presented in terms of mass percentages for defined size fractions, and the construction of cumulative distribution curves is emphasized. Use of trivial names such as “gravel” or “clay” is discouraged unless explicitly defined; precise size ranges should be reported.

Applications

• Environmental Science
  • Soil Quality Assessment: Critical for studies of soil function, contamination, and management.
  • Soil Monitoring: Supports long-term studies on land use change, erosion, or remediation.
• Agriculture
  • Determines soil structure, influencing water retention, aeration, and root development.
• Soil Classification and Mapping
  • Facilitates accurate classification of soils for land management, conservation, and research.
• Laboratory Analysis
  • Provides standardized procedures for routine soil testing in research and commercial laboratories.
• Foundations for Regulatory Compliance
  • Ensures soil particle size data meets the requirements of international or national regulations.

Related Standards

• ISO 565: Test sieves – Nominal sizes of openings.
• ISO 3310-1 & ISO 3310-2: Technical requirements and testing of test sieves (metal wire cloth and metal plate).
• ISO 11464: Soil quality – Pretreatment of samples for physico-chemical analysis.
• ISO 11265: Soil quality – Determination of specific electrical conductivity.

Practical Value

Implementing ISO 11277 ensures consistent, accurate, and internationally comparable soil particle size distribution results. This underpins reliable soil quality assessments, supports regulatory compliance, and enhances the comparability of research findings. The clear distinction between procedures for mineral and organic soil components, and the attention to sample preparation and reporting, empower practitioners in environmental, agricultural, and soil science fields to make informed, confident decisions based on robust data.

Keywords: ISO 11277, soil quality, particle size distribution, sieving, sedimentation, mineral soil, soil analysis, environmental science, soil assessment, laboratory testing.

SLOVENSKI STANDARD
01-oktober-2025
Kakovost tal - Določanje porazdelitve velikosti delcev v mineralnem delu tal -
Metoda s sejanjem in usedanjem
Soil quality - Determination of particle size distribution in mineral soil material - Method
by sieving and sedimentation
Qualité du sol - Détermination de la répartition granulométrique de la matière minérale
des sols - Méthode par tamisage et sédimentation
Ta slovenski standard je istoveten z: ISO/DIS 11277
ICS:
13.080.20 Fizikalne lastnosti tal Physical properties of soils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 11277
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
2025-05-23
and sedimentation
Voting terminates on:
2025-08-15
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
ICS: 13.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
This document is circulated as received from the committee secretariat.
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 11277:2025(en)
DRAFT
ISO/DIS 11277:2025(en)
International
Standard
ISO/DIS 11277
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
and sedimentation
Voting terminates on:
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
ICS: 13.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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This document is circulated as received from the committee secretariat. BE CONSIDERED IN THE LIGHT OF THEIR
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NOTIFICATION OF ANY RELEVANT PATENT
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 11277:2025(en)
ii
ISO/DIS 11277:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 2
6 Field sampling . 3
7 Sample preparation . 4
8 Dry sieving (material >2 mm) . 4
8.1 General .4
8.2 Apparatus .4
8.3 Procedure .5
8.4 Calculation and expression of results .6
9 Wet sieving and sedimentation (material <2 mm) . 6
9.1 General .6
9.2 Apparatus .6
9.3 Reagents .14
9.4 Calibrations . 15
9.4.1 Sampling pipette (see Figure 4) . 15
9.4.2 Dispersing-agent correction . 15
9.5 Test sample . 15
9.6 Destruction of organic matter .16
9.7 Removal of soluble salts and gypsum .17
9.8 Removal of carbonates .18
9.9 Removal of iron oxides .18
9.10 Dispersion .19
9.11 Wet sieving at 0,063 mm.19
9.12 Sedimentation .19
9.13 Calculation of results for fractions <2 mm . 20
10 Test report .21
Annex A (normative) Determination of particle size distribution of mineral soil material that
is not dried prior to analysis .22
Annex B (normative) Determination of particle size distribution of mineral soils by a
hydrometer method following destruction of organic matter .25
Annex C (informative) Precision of the method .34
Annex D (informative) Ultrasonic bath assisted wet sieving and sedimentation.36
Bibliography .38

iii
ISO/DIS 11277:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
This fourth edition cancels and replaces the third edition (ISO 11277:2020), which has been technically
revised and the first edition of ISO 11277:2020/Amd 1:2024. The main changes compared to the previous
edition are as follows:
— Incorporation of ISO 11277:2020/Amd 1:2024;
— Document has been editorially revised.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 11277:2025(en)
Introduction
The physical and chemical behaviour of soils is controlled in part by the amounts of mineral particles of
different sizes in the soil. The subject of this document is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral soil), within stated size classes.
The determination of particle size distribution is affected by organic matter, soluble salts, cementing agents
(like iron compounds), relatively insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree, upon drying, that the particle size distribution
of the dried material bears little or no relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those developed from recent volcanic
deposits, some highly weathered tropical soils, and soils often described as “cohesive” (see Reference [4]).
Other soils, such as the so-called “sub-plastic” soils of Australia, show little or no tendency to disperse under
normal laboratory treatments, despite field evidence of large clay content.
The procedures given in this document recognize these kinds of differences between soils from different
environments, and the methodology presented is designed to deal with them in a structured manner.
Such differences in soil behaviour can be very important, but awareness of them depends usually on local
knowledge. Given that the laboratory is commonly distant from the site of the field operation, the information
supplied by field teams becomes crucial to the choice of an appropriate laboratory procedure. This choice
can be made only if the laboratory is made fully aware of this background information.

v
DRAFT International Standard ISO/DIS 11277:2025(en)
Soil quality — Determination of particle size distribution in
mineral soil material — Method by sieving and sedimentation
WARNING — Persons using this document should be familiar with usual laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests, conducted in accordance with this document, be
carried out by suitably qualified staff.
1 Scope
This document specifies a basic method of determining the particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to
deal with the less common soils mentioned in the introduction. This document has been developed largely
for use in the field of environmental science, and its use in geotechnical investigations is something for
which professional advice might be required.
A major objective of this document is the determination of enough size fractions to enable the construction
of a reliable particle-size-distribution curve.
This document does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It
is also realized that the chemical pre-treatments and mechanical handling stages in this document could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary
particles, even though such primary particles could be better described as aggregates. If such disintegration
is undesirable, then this document is not used for the determination of the particle size distribution of such
weakly cohesive materials.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
ISO 11265, Soil quality — Determination of the specific electrical conductivity
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
3 Terms and definitions
There are no normative references in this document.

ISO/DIS 11277:2025(en)
4 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as
given below (the SI convention is followed for common units, e.g. g = gram; m = metre; mm = millimetre;
s = second, etc.).
Mg megagram (10 g)
5 Principle
The particle size distribution is determined by a combination of sieving and sedimentation, starting from
air-dried soil (see Reference [4]). A method for undried soil is given in Annex A. Particles not passing a 2 mm
aperture sieve are determined by dry sieving. Particles passing such a sieve, but retained on a 0,063 mm
aperture sieve, are determined by a combination of wet and dry sieving, whilst particles passing the latter
sieve are determined by sedimentation.
The pipette method is preferred. As an alternative, the hydrometer method is given in Annex B. A combination
of sieving and sedimentation enables the construction of a continuous particle-size-distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This document requires that
the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things
as the interaction of particles with electromagnetic radiation or electrical fields (see Reference [2]). There
are often considerable difficulties in relating the values obtained by these different methods for the same
sample. It is one of the intentions of this document that close adherence to its details should help minimize
interlaboratory variation in the determination of the particle size distribution of mineral soils. Therefore,
the proportions of fractions shall be determined only by weighing. If this is not the method used, then
conformance with this document cannot be claimed in the test report (see Clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder is
in accordance with Stokes's Law (see References [2], [4] and [7]), and the constraints that this implies, namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow, i.e. the Reynolds Number is less than about 0,2; this constraint sets
an upper equivalent spherical particle diameter (see below) slightly greater than 0,06 mm for Stokesian
settling under gravity (Reference [2]);
c) the suspension of particles is sufficiently dilute to ensure that no particle interferes with the settling of
any other particle;
d) there is no interaction between the particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is
of “infinite extent”;
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of equivalent spherical diameter. It is the principle upon which
the expression of the diameter of particles, as derived from sedimentation, is based in this document.
Stokes's Law can be written, for the purposes of this document, as in Formula (1):
 
th=−18ηρ/ ()ρ gd (1)
sw p
 
ISO/DIS 11277:2025(en)
where
t is the settling time, in seconds, of a particle of diameter d (see below);
p
η is the dynamic viscosity of water at the test temperature (see Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65 Mg/m ; see note);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken
w
as 1,00 Mg/m ; see note);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981 cm/s );
d is the equivalent spherical diameter of the particle of interest, in millimetres.
p
NOTE 1 It is realized that there are considerable differences between the densities of soil particles, but for the
purposes of this document it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m (Reference [8]),
3 3
as this is the commonest mineral in a very wide range of soils. The density of water is 0,998 2 Mg/m and 0,995 6 Mg/m
at 20 °C and 30 °C, respectively (see Reference [6]). Given the effect of the addition of a small amount of dispersant (see
9.3.2), the density of water is taken as 1,000 0 Mg/m over the permitted temperature range of this document (see 9.2.2).
Furthermore, for routine use, it is recommended that the sampling times be converted to minutes and/or
hours, as appropriate, to lessen the risk of error (see Table 3).
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand,
silt, etc. The meaning of such trivial names differs between countries, and in some cases there are no
exact translations of such words from one language to another; for example, the Dutch word “zavel” has no
equivalent in English. The only fraction for which there appears to be common agreement is clay, which is
defined as material of less than 0,002 mm equivalent spherical diameter (References [4]). Such trivial names
shall not be used in describing the results of particle size determination according to this document. Phrases
such as “. passing a 20 mm aperture sieve .” or “. less than 0,063 mm equivalent spherical diameter .”
shall be used instead. If trivial names shall be used, for example, to cross-reference to another International
or National Standard, then the trivial name should be defined explicitly, so as to remove any doubt as to
the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent spherical diameter) (see Clause 4).
Furthermore, it is common to use the word “texture” to describe the results of particle-size-distribution
measurements, e.g. “the particle size of this soil is of clay texture”. This is incorrect as the two concepts are
different, and the word “texture” shall not be used in the test report (see Clause 10) to describe the results
obtained by the use of this document.
6 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming > 10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
ISO/DIS 11277:2025(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Maximum size of material forming > 10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
6,3 0,5
5 0,2
2 or smaller 0,1
7 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm
aperture sieve. In this case, the test sample (9.5) can be taken either according to the procedures in ISO 11464 or from
the material passing a 2 mm aperture sieve according to 8.2.
8 Dry sieving (material >2 mm)
8.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives
the maximum mass which shall be retained on sieves of different diameters and apertures. If more than this
amount of material is retained, then it shall be subdivided appropriately and sieved again.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as
the sieve aperture, and the relationship between the various numbers is not immediately obvious. The use
of mesh numbers as a measurement of particle size is difficult to justify, and shall not be used in reporting
the results of this document.
8.2 Apparatus
8.2.1 Test sieves, with apertures according to ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (see Table 1 and 9.2.3).
The apertures chosen shall be stated in the test report (Clause 10). The accuracy of the sieves shall be verified
monthly against a set of master sieves kept for this purpose, using an accepted method such as particle
reference materials, microscopy, etc. (see Reference [2]) depending on the sieve aperture. Tolerances shall
meet the requirements of ISO 3310-1 and ISO 3310-2. Sieves that do not meet these specifications shall be
discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended
for the larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly
when in regular use, and on every occasion if used less often. A record shall be kept of such inspections.
Round-hole sieves shall not be used.
8.2.2 Balance, capable of weighing to an accuracy of within ±0,5 g.
8.2.3 Mechanical sieve shaker.
It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very
heavy-duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller
apertures.
8.2.4 A sieve brush and a stiff brush.

ISO/DIS 11277:2025(en)
8.2.5 Ultrasonic bath, able to provide an acoustic power P (W) level in the range of 5 W to 20 W per litre
ac
of water (see Annex D), typically operating at a frequency between 37 kHz to 45 kHz.
8.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the
weighed material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the
stiff brush (to remove any adhering soil), sieve the material. Take care not to detach any fragments from the
primary particles. Sieve the retained material on the nest of sieves of selected apertures (8.2.1) and record
the amount retained on each sieve to the nearest 0,5 g. Do not overload the sieves (see Table 1) but sieve the
material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (see Table 2)
2 3
obtained by an appropriate subsampling method (see Clause 6), and place this on a nest of sieves, the
lowermost having an aperture of 2 mm. Shake the sieves mechanically until no further material passes any
of the sieves (see Note). Record the mass of material retained on each sieve and the mass passing the 2 mm
aperture sieve.
The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for
2 3
sieve damage and discard sieves as appropriate (see 8.2.1).
NOTE For practical purposes, it is usual to choose a standard sieve shaking time which gives an acceptable degree
of sieving efficiency with a wide range of soil materials. The minimum recommended period is 10 min.
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Test sieve Maximum mass
aperture
kg
Sieve diameter
mm
mm 450 400 300 200 100
50 10 8,9 4,5 — —
37,5 8 7,1 3,5 — —
28 6 5,3 2,5 — —
20 4 3,6 2 — —
14 3 2,7 1,5 — —
10 2 1,8 1 — —
6,3 1,5 1,3 0,75 — —
5 1 0,9 0,5 — —
3,35 — — 0,3 0,15
2 — — 0,2 0,1
1,18 — — 0,1 0,05
0,6 — — 0,075 0,037 5
0,425 — — 0,075 0,037 5
0,3 — — 0,05 0,025
0,212 — — 0,05 0,025
0,15 — — 0,04 0,02
0,063 — — 0,025 0,012 5
ISO/DIS 11277:2025(en)
8.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained
by each sieve as a proportion of m . For example (Formula (2)):
Proportionretainedonthem20 msieve=[]mm()20mm / (2)
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by m /m and
2 3
calculate this as a proportion of m . For example (Formula (3)):
Proportionretainedonthem63,,msieve= mm()63mm []()//mm (3)
23 1
Present the results as a Table showing, to two significant figures, the proportion by mass retained on each
sieve and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative
distribution curve (see Figure 1).
9 Wet sieving and sedimentation (material <2 mm)
9.1 General
This clause specifies the procedure (see Figure 2) for the determination of the particle size distribution of
the material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see note).
In order to ensure that primary particles, rather than loosely bonded aggregates, are measured, organic
matter and salts are removed, especially sparingly soluble salts such as gypsum which would otherwise
prevent dispersion and/or promote flocculation of the finer soil particles in suspension (see 9.6), and a
dispersing agent is added (9.3.2). These procedures are required in this document, and their omission shall
invalidate its application. Sometimes iron oxides and carbonates, especially of calcium and/or magnesium,
are also removed. Preferred procedures for the removal of these compounds are given in the note in 9.7. The
removal of any compound shall be recorded in the test report (see Clause 10).
NOTE 1 Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent
spherical diameter. However, the method cannot be used to divide this class further with reliability, as particles less
than about 0,001 mm equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian motion
(see Reference [2]).
9.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in
batches. Experience has shown (see Reference [7]) that one operator can process up to 36 samples in a batch
at a time, given sufficient apparatus and space, especially if calculations are dealt with by a computer.
9.2.1 Sampling pipette or sampling needle, of a pattern similar to that shown in Figure 3 with sideways
openings, the chief requirement being that the smallest practicable horizontal zone of sedimenting
suspension shall be sampled. The pipette shall be of not less than 10 ml volume and shall be held in a frame
so that it can be lowered to a fixed depth within a sedimentation tube (see Figure 4).
NOTE 1 Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes.
A 25 ml volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be found to
be sufficient for soils with down to about 10 % mass fraction of <0,063 mm equivalent spherical diameter. Below this
amount, greater precision is likely to be obtained with a pipette of larger volume.
NOTE 2 The position of the pipette is adjusted to the new suspension surface after each sampling.
NOTE 3 Automated systems can be used, if the results are proven to be equivalent.

ISO/DIS 11277:2025(en)
Figure 1 — Particle-size-distribution chart

ISO/DIS 11277:2025(en)
Figure 2 — Flow chart
ISO/DIS 11277:2025(en)
Dimensions in millimetres
Key
1 bulb capacity: approximately 125 ml

ISO/DIS 11277:2025(en)
2 pipette and changeover cock capacity at least 10 ml
3 sideways opening
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 3 — Sampling pipette for sedimentation test

ISO/DIS 11277:2025(en)
Key
A and B 125 ml bulb funnel with stopcock H sedimentation tube
C safety-bulb suction inlet tube 1 scale graduated in millimetres
D safety bulb 2 clamps
E tap 3 sliding panel
ISO/DIS 11277:2025(en)
F outlet tube 4 constant-temperature bath
G sampling pipette
a
D, F and G are joined to three-way stopcock E.
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
9.2.2 Constant-temperature room or bath, which can be maintained at between 20 °C and (30 ± 1) °C.
If a bath is used, it shall accept a sedimentation tube immersed to the 500 ml or 1 000 ml mark and shall not
vibrate the contents of the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that
activity does not cause the tubes and their contents to vibrate.
NOTE This temperature range has been chosen to allow for the difficulties of maintaining one specified
temperature in different parts of the world. In addition, the lower temperature gives sedimentation times that fit well
into an average working day, whilst the upper temperature still allows for a sensible settling time for the fraction
0,063 mm equivalent spherical diameter (see Clause 4 and Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m ) at a sampling depth
p
from the surface of (100 ± 1) mm at different temperatures assuming a particle density of 2,65 Mg/
3 3
m and density of water with dispersant of 1,00 Mg/m
Times, after mixing, of starting sampling operation
st a nd rd th
T η 1 sample 2 sample 3 sample 4 sample
°C mPa/s min s min s min s h min s
15 1,139 1 4 5 17 53 11 8 47 45
16 1,109 1 2 5 8 51 47 8 33 51
17 1,081 1 1 5 1 50 29 8 20 53
18 1,053 0 59 4 53 49 10 8 7 54
19 1,027 0 58 4 46 47 57 7 55 52
20 1,002 0 56 4 38 46 46 7 44 5
21 0,978 0 55 4 32 45 39 7 32 55
22 0,955 0 53 4 25 44 34 7 22 16
23 0,933 0 52 4 19 43 33 7 12 4
24 0,911 0 51 4 13 42 32 7 1 58
25 0,891 0 50 4 8 41 35 6 52 37
26 0,871 0 49 4 2 40 39 6 43 21
27 0,851 0 48 3 56 39 43 6 34 5
28 0,833 0 47 3 51 38 53 6 25 44
29 0,815 0 46 3 46 38 2 6 17 24
30 0,798 0 45 3 42 37 14 6 9 31
31 1,781 0 44 3 37 36 27 6 1 39
32 0,764 0 43 3 33 35 42 5 54 11
33 0,749 0 42 3 28 34 58 5 46 57
34 0,734 0 41 3 24 34 16 5 39 58
35 0,719 0 40 3 20 33 35 5 33 12
d (mm) 0,063 0,02 0,006 3 0,002
p
Sampling depth (m) 0,2 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1
a Sampling depth (200 ± 1) mm to allow adequate time for the stabilization of the suspension after mixing.

ISO/DIS 11277:2025(en)
9.2.3 Glass sedimentation tubes, without pouring lips, of internal diameter approximately 50 - 60 mm,
and overall length of approximately 350 mm – 450 mm, graduated at 500 ml or 1 000 ml volume, and with
either rubber bungs to fit or a stirrer.
9.2.4 Stirrer, of non-corrodible material.
9.2.5 Weighing vessels, inert material, with masses known to the nearest 0,000 1 g.
9.2.6 Mechanical shaker, capable of keeping 30 g of soil in suspension in 150 ml of liquid.
NOTE For keeping the soil in suspension, a suitable device could be an end-to-end type of shaker (e.g. 10 to
30 revolutions/min) or a stirrer.
9.2.7 Test sieves, complying with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and
0,063 mm, plus two intermediate sieves. The test report shall state which apertures are used. Round-hole
sieves shall not be used.
NOTE The choice of the sieve of aperture 0,063 mm given here is for illustration but accords with the widespread
use of this particle size to define the upper boundary of the silt fraction. Local requirements can specify another
aperture. The choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests
that sieves of aperture close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
9.2.8 Suitable sampledivider (see Clause 6).
9.2.9 Balance, capable of weighing to an accuracy of within ±0,000 1 g.
9.2.10 Drying oven, capable of maintaining a temperature between 105 °C and 110 °C.
9.2.11 Stop clock, readable to 1 s.
9.2.12 Desiccator, containing anhydrous silica gel (preferably of the self-indicating type), capable of
holding the five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and
110 °C when it is no longer effective.
9.2.13 Glass beaker, of capacity 650 ml with a cover glass to fit, or a 300 to 500 ml centrifuge bottle with
a leak proof cap.
NOTE This apparatus is used for chemical pre-treatment during which a constant problem is the adhesion of very
fine particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone
centrifuge bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide
and common dispersing agents. Their use can also save significant amounts of operator time.
9.2.14 Centrifuge, capable of holding the 300 to 500 ml centrifuge bottles (see 9.2.13).
9.2.15 Measuring cylinder, of capacity 1 000 ml.
9.2.16 Pipette, of capacity between 10 to 50 ml (25 ml recommended) (see 8.2.1).
9.2.17 Glass filter funnel, capable of holding the 0,063 mm sieve.
9.2.18 Wash bottle containing water (see 8.3).
9.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber
sleeve at one end.
ISO/DIS 11277:2025(en)
9.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C or Water bath,
capable of maintaining a temperature between 90 °C and 95 °C.
NOTE A hotplate is essential if polymer centrifuge bottles are used for the chemical pretreatment, but a Bunsen
burner, gauze and tripod are sufficient if glass beakers are used.
9.2.21 Suction device, similar to that shown in Figure 5 is useful, but not essential.
Key
1 flexible tube
2 pasteur pipette or similar
3 reservoir (5 l or 10 l)
a
To vacuum.
Figure 5 — Sketch of suction device
9.2.22 Sieve brush.
9.2.23 Electrical conductivity meter, accurate to 1 mS/m.
9.3 Reagents
All reagents shall be of recognized analytical grade. Use water having an electrical conductivity no greater
than 10 mS/m at 25 °C at the time of use.
9.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE A 30 % volume fraction solution is one which will yield 30 ml of gaseous oxygen from 100 ml of solution
(under standard conditions of temperature and pressure) upon reduction to water, either by chemical means or by
boiling.
ISO/DIS 11277:2025(en)
9.3.2 Solution of a dispersing agent.
As a dispersing agent, dissolve 33 g of sodium hexametaphosphate and 7 g of anhydrous sodium carbonate
in water to make 1 l of solution. Store away from strong sunlight and preferably in a dark bottle. Record the
date of preparation on the bottle. The solution is unstable and shall be replaced after one month.
Another suitable dispersant is 0,1 M sodium pyrophosphate solution (tetrasodiumdiphosphate decahydrate
Na P O · 10 H O).
4 2 7 2
The sodium carbonate buffers the solution and the suspension of the soil, to about pH 9,8. The described
dispersing agents have been found successful with a very wide range of soils. However, if there are signs that
dispersion is ineffective, consider firstly that flocculating salts might be present (see 9.7). If dispersion is still
unsuccessful after removal of salts, then other dispersing agents should be considered. A very effective but
less widely used dispersing agent is prepared by replacing the sodium carbonate with 20 % volume fraction
ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the hexametaphosphate solution. There
are many other dispersing agents (see Reference [3]). Whichever is chosen, considerable investigation will
be required to establish
...

FINAL DRAFT
International
Standard
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
2026-09-25
and sedimentation
Voting terminates on:
2026-11-20
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
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INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
and sedimentation
Voting terminates on:
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 3
6 Field sampling . 4
7 Sample preparation . 5
8 Dry sieving (material >2 mm) . 5
8.1 General .5
8.2 Apparatus .5
8.3 Procedure .5
8.4 Calculation and expression of results .7
9 Wet sieving and sedimentation (material <2 mm) . 7
9.1 General .7
9.2 Apparatus .7
9.3 Reagents .14
9.4 Calibrations . 15
9.4.1 Sampling pipette. 15
9.4.2 Dispersing-agent correction . 15
9.5 Test sample . 15
9.6 Destruction of organic matter .16
9.7 Removal of soluble salts and gypsum .17
9.8 Removal of carbonates .18
9.9 Removal of iron oxides .18
9.10 Dispersion .19
9.11 Wet sieving at 0,063 mm.19
9.12 Sedimentation .19
9.13 Calculation of results for fractions <2 mm . 20
10 Test report .21
Annex A (informative) Determination of particle size distribution of mineral soil material that
is not dried prior to analysis .22
Annex B (informative) Determination of particle size distribution of mineral soils by a
hydrometer method following destruction of organic matter .25
Annex C (informative) Precision of the method .32
Annex D (informative) Ultrasonic bath assisted wet sieving and sedimentation.34
Bibliography .36

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
This fourth edition cancels and replaces the third edition (ISO 11277:2020), which has been technically
revised. It also incorporates the Amendment ISO 11277:2020/Amd 1:2024.
The main changes are as follows:
— the recommendation to remove organic substances has been changed to a requirement (only for the
determination of ecologically relevant particle size distribution the destruction of organic matter is not
necessary);
— systems operating with ultrasonic treatments are only allowed under restricted conditions.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The physical and chemical behaviour of soils is controlled in part by the amounts of mineral particles of
different sizes in the soil. The subject of this document is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral soil), within stated size classes.
The determination of particle size distribution is affected by organic matter, soluble salts, cementing agents
(such as iron compounds), relatively insoluble substances such as carbonates and sulfates, or combinations
of these. Some soils change their behaviour to such a degree, upon drying, that the particle size distribution
of the dried material bears little or no relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those developed from recent volcanic
deposits, some highly weathered tropical soils, and soils often described as “cohesive” (see Reference [4]).
Other soils, such as the so-called “sub-plastic” soils of Australia, show little or no tendency to disperse under
normal laboratory treatments, despite field evidence of large clay content.
The procedures given in this document recognize these kinds of differences between soils from different
environments, and the methodology presented is designed to deal with them in a structured manner.
Such differences in soil behaviour can be very important, but awareness of them depends usually on local
knowledge. Given that the laboratory is commonly distant from the site of the field operation, the information
supplied by field teams becomes crucial to the choice of an appropriate laboratory procedure. This choice
can be made only if the laboratory is made fully aware of this background information.

v
FINAL DRAFT International Standard ISO/FDIS 11277:2026(en)
Soil quality — Determination of particle size distribution in
mineral soil material — Method by sieving and sedimentation
WARNING — Persons using this document should be familiar with usual laboratory practice. This
document does not purport to address all safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — Tests conducted in accordance with this document shall be carried out by suitably
trained staff.
1 Scope
This document specifies a basic method of determining the particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to
deal with the less common soils mentioned in the introduction. This document has been developed largely
for use in the field of environmental science, and its use in geotechnical investigations is something for
which professional advice might be required.
A major objective of this document is the determination of enough size fractions to enable the construction
of a reliable particle-size-distribution curve.
This document does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It
is also realized that the chemical pre-treatments and mechanical handling stages in this document could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary
particles, even though such primary particles could be better described as aggregates. If such disintegration
is undesirable, then this document is not used for the determination of the particle size distribution of such
weakly cohesive materials.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ISO 11265, Environmental solid matrices — Determination of the specific electrical conductivity
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at https:// www .electropedia .org/
3.1
diameter of a particle
diameter of a sphere whose behaviour in suspension matches that of the particle
4 Symbols
The following symbols are used in this document.
C specific heat of the liquid (4,18 J/g·K for water)
P
d equivalent spherical diameter of the particle of interest mm
p
2 2
g acceleration due to gravity (981 cm/s ) cm/s
γ electrical conductivity mS/m
c
h height of the bulb mm
H length from the neck of the bulb to graduation d mm
L distance between the graduation marks on the measuring cylinder mm
L’ observed hydrometer reading
m mass of solid material in 500 ml of dispersant solution g
d
m mass of residue g
r
m sample mass g
t
m mass of solid in suspension in 500 ml g
fx
m mass of material from the xth pipette sampling g
sx
M mass of liquid g
η dynamic viscosity of water at the test temperature (as shown in Table B.2) mPa/s
P proportion
P proportion of material <2 mm in the total soil
s
P proportion of the fraction <2 mm
t
P proportion in total soil mass
tsm
P proportion retained on the 6,3 mm sieve
6,3
P proportion retained on the 16 mm sieve
P proportion retained on the 20 mm sieve
p delivered acoustic power
ac
3 3
ρ mean particle density (2,65 Mg/m , see the note in Clause 4); Mg/m
s
3 3
ρ density of the suspension liquid (1,00 Mg/m , see the note in Clause 4); Mg/m
w
t elapsed time s
Δt time s
ΔT temperature K
V calibrated volume of the pipette ml
c
V volume of the hydrometer bulb ml
h
V indicated volume of the measuring cylinder between the graduations used in the deter- ml
L
mination of L
z effective depth at which the density of the suspension is measured mm
z meniscus correction
m
5 Principle
The particle size distribution is determined by a combination of sieving and sedimentation, starting from
air-dried soil (see Reference [4]). A method for undried soil is given in Annex A. Particles not passing a 2 mm
aperture sieve are determined by dry sieving. Particles passing a 2 mm aperture sieve, but retained on
a 0,063 mm aperture sieve, are determined by a combination of wet and dry sieving. Particles passing a
0,063 mm aperture sieve are determined by sedimentation.
NOTE 1 The test sieves are specified as type of metal wire cloth.
The pipette method is preferred. As an alternative, the hydrometer method is given in Annex B. A combination
of sieving and sedimentation enables the construction of a continuous particle-size-distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This document requires that
the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things
as the interaction of particles with electromagnetic radiation or electrical fields (see Reference [2]). There
are often considerable difficulties in relating the values obtained by these different methods for the same
sample. It is one of the intentions of this document that close adherence to its details should help minimize
interlaboratory variation in the determination of the particle size distribution of mineral soils. Therefore,
the proportions of fractions shall be determined only by weighing. If this is not the method used, then
conformance with this document cannot be claimed in the test report (see Clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder
is in accordance with Stokes’s Law (see References [2], [4] and [7]), and the constraints that this implies,
namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow, i.e. the Reynolds number is less than approximately 0,2; this
constraint sets an upper equivalent spherical particle diameter (see below) slightly greater than
0,06 mm for Stokesian settling under gravity (Reference [2]);
c) the suspension of particles is sufficiently diluted to ensure that no particle interferes with the settling
of any other particle;
d) there is no interaction between the particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is
of “infinite extent”;
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.

Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of equivalent spherical diameter. It is the principle upon
which the expression of the diameter of particles, as derived from sedimentation, is based in this document.
Stokes’s Law can be written, for the purposes of this document, as in Formula (1):
 
th18/  gd (1)

sw p
 
NOTE 2 It is realized that there are considerable differences between the densities of soil particles, but for the
purposes of this document it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m (Reference [8]),
as this is the commonest mineral in a very wide range of soils. The density of water is 0,998 2 Mg/m and 0,995 6 Mg/
m at 20 °C and 30 °C, respectively (see Reference [6]). Given the effect of the addition of a small amount of dispersant
(see 9.3.2), the density of water is taken as 1,000 0 Mg/m over the permitted temperature range of this document (see
9.2.2).
Furthermore, for routine use, it is recommended that the sampling times be converted to minutes or hours,
or both, as appropriate, to lessen the risk of error (see Table 3).
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand,
silt, etc. The meaning of such trivial names differs between countries, and in some cases, there are no
exact translations of such words from one language to another; for example, the Dutch word “zavel” has no
equivalent in English. The only fraction for which there appears to be common agreement is clay, which is
defined as material of less than 0,002 mm equivalent spherical diameter (References [4]). Such trivial names
shall not be used in describing the results of particle size determination according to this document. Phrases
such as “. passing a 20 mm aperture sieve .” or “. less than 0,063 mm equivalent spherical diameter .”
shall be used instead. If trivial names are used, for example, to cross-reference to another International or
National Standard, then the trivial name should be defined explicitly, to remove any doubt as to the meaning
intended, e.g. silt (0,063 mm to 0,002 mm equivalent spherical diameter) (see Clause 4). Furthermore, it is
common to use the word “texture” to describe the results of particle-size-distribution measurements, e.g.
“the particle size of this soil is of clay texture”. This is incorrect as the two concepts are different, and the
word “texture” shall not be used in the test report (see Clause 10) to describe the results obtained using this
document.
6 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming >10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
6,3 0,5
5 0,2
2 or smaller 0,1
7 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm
aperture sieve. In this case, the test sample (9.5) can be taken either according to the procedures in ISO 11464 or from
the material passing a 2 mm aperture sieve according to 8.2.
8 Dry sieving (material >2 mm)
8.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives
the maximum mass which shall be retained on sieves of different diameters and apertures. If more than this
amount of material is retained, then it shall be subdivided appropriately and sieved again.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as
the sieve aperture, and the relationship between the various numbers is not immediately obvious. The use
of mesh numbers as a measurement of particle size is difficult to justify and shall not be used in reporting
the results of the procedures described in this document.
8.2 Apparatus
8.2.1 Test sieves, with apertures according to ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (see Table 1 and 8.2.3).
The apertures chosen shall be stated in the test report (Clause 10). The accuracy of the sieves shall be verified
monthly against a set of master sieves kept for this purpose, using an accepted method such as particle
reference materials, microscopy, etc. (see Reference [2]) depending on the sieve aperture. Tolerances shall
meet the requirements of ISO 3310-1 and ISO 3310-2. Sieves that do not meet these specifications shall be
discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended
for the larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly
when in regular use, and on every occasion if used less often. A record shall be kept of such inspections.
Round-hole sieves shall not be used.
8.2.2 Balance, capable of weighing to an accuracy of within ±0,5 g.
8.2.3 Mechanical sieve shaker.
It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very
heavy-duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller
apertures.
8.2.4 A sieve brush and a stiff brush.
8.2.5 Ultrasonic bath, able to provide an acoustic power p (W) level in the range of 5 W to 20 W per litre
ac
of water (see Annex D), typically operating at a frequency between 37 kHz to 45 kHz.
8.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the
weighed material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the
stiff brush (to remove any adhering soil), sieve the material. Take care not to detach any fragments from the

primary particles. Sieve the retained material on the nest of sieves of selected apertures (8.2.1) and record
the amount retained on each sieve to the nearest 0,5 g. Do not overload the sieves (see Table 1) but sieve the
material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (see Table 2)
2 3
obtained by an appropriate subsampling method (see Clause 6), and place this on a nest of sieves, the
lowermost having an aperture of 2 mm. Shake the sieves mechanically until no further material passes any
of the sieves. Record the mass of material retained on each sieve and the mass passing the 2 mm aperture
sieve.
The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check
2 3
for sieve damage and discard sieves as appropriate (see 8.2.1). For practical purposes, a standard sieve
shaking time should be chosen which gives an acceptable degree of sieving efficiency with a wide range of
soil materials.
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Test sieve Maximum mass
aperture
kg
Sieve diameter
mm
mm 450 400 300 200 100
50 10 8,9 4,5 — —
37,5 8 7,1 3,5 — —
28 6 5,3 2,5 — —
20 4 3,6 2 — —
14 3 2,7 1,5 — —
10 2 1,8 1 — —
6,3 1,5 1,3 0,75 — —
5 1 0,9 0,5 — —
3,35 — — — 0,3 0,15
2 — — — 0,2 0,1
1,18 — — — 0,1 0,05
0,6 — — — 0,075 0,037 5
0,425 — — — 0,075 0,037 5
0,3 — — — 0,05 0,025
0,212 — — — 0,05 0,025
0,15 — — — 0,04 0,02
0,063 — — — 0,025 0,012 5
8.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained
by each sieve as a proportion of m . For example, as in Formula (2):
Pm20mm /m (2)
20 1
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by m /m and
2 3
calculate this as a proportion of m . For example, as in Formula (3):
Pm 63,/mm mm /m (3)
63, 23 1
Present the results as a Table showing, to two significant figures, the proportion by mass retained on each
sieve and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative
distribution curve (see Figure 1).
9 Wet sieving and sedimentation (material <2 mm)
9.1 General
This clause specifies the procedure (see Figure 2) for the determination of the particle size distribution
of the material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see
NOTE). In order to ensure that primary particles, rather than loosely bonded aggregates, are measured,
organic matter and salts are removed, especially sparingly soluble salts such as gypsum which would
otherwise prevent either dispersion or promote flocculation of the finer soil particles in suspension, or both
(see 9.6), and a dispersing agent is added (9.3.2). These procedures are required in this document, and their
omission shall invalidate its application. Sometimes iron oxides and carbonates, especially of calcium and/
or magnesium, are also removed. Preferred procedures for the removal of these compounds are given in the
notes in 9.7, 9.8 and 9.9. The removal of any compound shall be recorded in the test report (see Clause 10).
NOTE Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent
spherical diameter. However, the method cannot be used to divide this class further with reliability, as particles
less than approximately 0,001 mm equivalent spherical diameter can be kept in suspension almost indefinitely by
Brownian motion (see Reference [2]).
9.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in
batches. Experience has shown (see Reference [7]) that one operator can process up to 36 samples in a batch
at a time, given sufficient apparatus and space, especially if calculations are dealt with by a computer.
9.2.1 Sampling pipette or sampling needle, of a pattern similar to that shown in Figure 3 with sideways
openings. The smallest practicable horizontal zone of sedimenting suspension shall be sampled. The pipette
shall be of not less than 10 ml volume and shall be held in a frame so that it can be lowered to a fixed depth
within a sedimentation tube (see Figure 4).
NOTE 1 Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes.
A 25 ml volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be sufficient
for soils with down to approximately 10 % mass fraction of <0,063 mm equivalent spherical diameter. Below this
amount, greater precision is likely to be obtained with a pipette of larger volume.
NOTE 2 The position of the pipette is adjusted to the new suspension surface after each sampling.
NOTE 3 Automated systems can be used, if the results are proven to be equivalent.

Figure 1 — Particle-size-distribution chart

Figure 2 — Flow chart of the soil sample pretrement procedure to determine
particle size of mineral soil
Dimensions in millimetres
Key
1 bulb (capacity: approximately 125 ml)
2 pipette and changeover cock (capacity at least 10 ml)
3 sideways opening
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 3 — Sampling pipette for sedimentation test

Key
1 and 2 125 ml bulb funnel with stopcock
3 safety-bulb suction inlet tube
4 safety bulb
5 tap
6 outlet tube
7 sampling pipette
8 sedimentation tube
9 scale graduated in millimetres
10 clamps
11 sliding panel
12 constant-temperature bath
a
4, 6 and 7 are joined to three-way stopcock 5.
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
9.2.2 Constant-temperature room or bath, which can be maintained at between 20 °C and (30 ± 1) °C.
If a bath is used, it shall accept a sedimentation tube immersed to the 500 ml or 1 000 ml mark and shall not
vibrate the contents of the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that
activity does not cause the tubes and their contents to vibrate.
NOTE This temperature range has been chosen to allow for the difficulties of maintaining one specified
temperature in different parts of the world. In addition, the lower temperature gives sedimentation times that fit well
into an average working day, whilst the upper temperature still allows for a sensible settling time for the fraction
0,063 mm equivalent spherical diameter (see Clause 4 and Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m ) at a sampling depth
p
from the surface of (100 ± 1) mm at different temperatures assuming a particle density of 2,65 Mg/
3 3
m and density of water with dispersant of 1,00 Mg/m
Times, after mixing, of starting sampling operation
st a nd rd th
T η 1 sample 2 sample 3 sample 4 sample
°C mPa/s min s min s min s h min s
15 1,139 1 4 5 17 53 11 8 47 45
16 1,109 1 2 5 8 51 47 8 33 51
17 1,081 1 1 5 1 50 29 8 20 53
18 1,053 0 59 4 53 49 10 8 7 54
19 1,027 0 58 4 46 47 57 7 55 52
20 1,002 0 56 4 38 46 46 7 44 5
21 0,978 0 55 4 32 45 39 7 32 55
22 0,955 0 53 4 25 44 34 7 22 16
23 0,933 0 52 4 19 43 33 7 12 4
24 0,911 0 51 4 13 42 32 7 1 58
25 0,891 0 50 4 8 41 35 6 52 37
26 0,871 0 49 4 2 40 39 6 43 21
27 0,851 0 48 3 56 39 43 6 34 5
28 0,833 0 47 3 51 38 53 6 25 44
29 0,815 0 46 3 46 38 2 6 17 24
30 0,798 0 45 3 42 37 14 6 9 31
31 1,781 0 44 3 37 36 27 6 1 39
32 0,764 0 43 3 33 35 42 5 54 11
33 0,749 0 42 3 28 34 58 5 46 57
34 0,734 0 41 3 24 34 16 5 39 58
35 0,719 0 40 3 20 33 35 5 33 12
d (mm) 0,063 0,02 0,006 3 0,002
p
Sampling depth (m) 0,2 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1
a
Sampling depth (200 ± 1) mm to allow adequate time for the stabilization of the suspension after mixing.

9.2.3 Glass sedimentation tubes, without pouring lips, of internal diameter approximately
50 mm to 60 mm, and overall length of approximately 350 mm to 450 mm, graduated at 500 ml or 1 000 ml
volume, and with either rubber bungs to fit or a stirrer.
9.2.4 Stirrer, of non-corrodible material.
9.2.5 Weighing vessels, inert material, with masses known to the nearest 0,000 1 g.
9.2.6 Mechanical shaker, capable of keeping 30 g of soil in suspension in 150 ml of liquid.
NOTE For keeping the soil in suspension, a suitable device could be an end-to-end type of shaker [e.g. (10 to
30) revolutions/min] or a stirrer.
9.2.7 Test sieves, conforming with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and
0,063 mm, plus two intermediate sieves. The test report shall state which apertures are used. Round-hole
sieves shall not be used.
NOTE The choice of the sieve of aperture 0,063 mm given here is for illustration but accords with the widespread
use of this particle size to define the upper boundary of the silt fraction. Local requirements can specify another
aperture. The choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests
that sieves of aperture close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
9.2.8 Suitable sampledivider (see Clause 6).
9.2.9 Balance, capable of weighing to an accuracy of within ±0,000 1 g.
9.2.10 Drying oven, capable of maintaining a temperature between 105 °C and 110 °C.
9.2.11 Stop clock, readable to 1 s.
9.2.12 Desiccator, containing anhydrous silica gel (preferably of the self-indicating type), capable of
holding the five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and
110 °C when it is no longer effective.
9.2.13 Glass beaker, of capacity 650 ml with a cover glass to fit, or a 300 to 500 ml centrifuge bottle with
a leak proof cap.
NOTE This apparatus is used for chemical pre-treatment during which a constant problem is the adhesion of very
fine particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone
centrifuge bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide
and common dispersing agents. Their use can also save significant amounts of operator time.
9.2.14 Centrifuge, capable of holding the 300 ml to 500 ml centrifuge bottles (see 9.2.13).
9.2.15 Measuring cylinder, of capacity 1 000 ml.
9.2.16 Pipette, of capacity between 10 ml to 50 ml (25 ml recommended) (see 8.2.1).
9.2.17 Glass filter funnel, capable of holding the 0,063 mm sieve.
9.2.18 Wash bottle containing water (see 8.3).
9.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber
sleeve at one end.
9.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C or water bath,
capable of maintaining a temperature between 90 °C and 95 °C. A hotplate is essential if polymer centrifuge
bottles are used for the chemical pretreatment, but a Bunsen burner, gauze and tripod are sufficient if glass
beakers are used.
9.2.21 Suction device, similar to that shown in Figure 5 is useful, but not essential.
Key
1 flexible tube
2 pasteur pipette or similar
3 reservoir (5 l or 10 l)
a
To vacuum.
Figure 5 — Suction device
9.2.22 Sieve brush.
9.2.23 Electrical conductivity meter, accurate to 1 mS/m.
9.3 Reagents
All reagents shall be of recognized analytical grade. Use water having an electrical conductivity no greater
than 10 mS/m at 25 °C at the time of use.
9.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE A 30 % volume fraction solution is one which yields 30 ml of gaseous oxygen from 100 ml of solution (under
standard conditions of temperature and pressure) upon reduction to water, either by chemical means or by boiling.
9.3.2 Solution of a dispersing agent.
As a dispersing agent, dissolve 33 g of sodium hexametaphosphate and 7 g of anhydrous sodium carbonate
in water to make 1 l of solution. Store away from strong sunlight and preferably in a dark bottle. Record the
date of preparation on the bottle. The solution is unstable and shall be replaced after one month.

Another suitable dispersant is 0,1 M sodium pyrophosphate solution (tetrasodiumdiphosphate decahydrate
Na P O · 10 H O).
4 2 7 2
The sodium carbonate buffers the solution and the suspension of the soil, to approximately pH 9,8. The
described dispersing agents have been found successful with a very wide range of soils. However, if there
are signs that dispersion is ineffective, consider firstly that flocculating salts might be present (see 9.7). If
dispersion is still unsuccessful after removal of salts, then other dispersing agents should be considered.
A very effective but less widely used dispersing agent is prepared by replacing the sodium carbonate
with 20 % volume fraction ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the
hexametaphosphate solution. There are many other dispersing agents (see Reference [3]). Whichever is
chosen, considerable investigation will be required to establish its effectiveness. It is noticed that some soils
show fewer problems of dispersion if analysed without drying (see Annex A). Some soils derived from recent
volcanic deposits will disperse more effectively in an acid medium (see Reference [10]).
9.3.3 Octan-2-ol, or a similar volatile antifoaming agent.
Octan-2-ol is highly effective and relatively long-lasting. Ethanol or methanol can also be used, but the use of
pentan-2-ol (amyl alcohol) is discouraged because it is potentially addictive.
9.4 Calibrations
9.4.1 Sampling pipette
Clean and dry the pipette (see Figure 4) thoroughly and immerse the tip in water held at the same temperature
as that of the constant-temperature environment (9.2.2). By means of a tube attached to the safety-bulb
suction inlet tube (item 3 in Figure 4), draw wa
...

ISO/TC 190/SC 3/WG 14
Secretariat: DIN
Date: 2026-07-09-11
Soil quality — Determination of particle size distribution in mineral
soil material — Method by sieving and sedimentation
Qualité du sol — Détermination de la répartition granulométrique de la matière minérale des sols — Méthode
par tamisage et sédimentation
FDIS stage
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland.
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 3
6 Field sampling . 4
7 Sample preparation . 5
8 Dry sieving (material >2 mm) . 5
8.1 General . 5
8.2 Apparatus . 5
8.3 Procedure . 6
8.4 Calculation and expression of results . 7
9 Wet sieving and sedimentation (material <2 mm) . 7
9.1 General . 7
9.2 Apparatus . 8
9.3 Reagents . 21
9.4 Calibrations . 21
9.5 Test sample . 22
9.6 Destruction of organic matter . 23
9.7 Removal of soluble salts and gypsum . 24
9.8 Removal of carbonates . 24
9.9 Removal of iron oxides . 25
9.10 Dispersion . 25
9.11 Wet sieving at 0,063 mm . 26
9.12 Sedimentation . 26
9.13 Calculation of results for fractions <2 mm . 27
10 Test report . 28
Annex A (informative) Determination of particle size distribution of mineral soil material that
is not dried prior to analysis . 29
Annex B (informative) Determination of particle size distribution of mineral soils by a
hydrometer method following destruction of organic matter . 32
Annex C (informative) Precision of the method . 43
Annex D (informative) Ultrasonic bath assisted wet sieving and sedimentation . 45
Bibliography . 47

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO'sISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
This fourth edition cancels and replaces the third edition (ISO 11277:2020), which has been technically
revised. It also incorporates the Amendment ISO 11277:2020/Amd. 1:2024.
The main changes are as follows:
— — Thethe recommendation to remove organic substances shall be removed. Onlyhas been changed to a
requirement (only for the determination of ecologically relevant particle size distribution the destruction
of organic matter is not necessary.);
— — Systemssystems operating with ultrasonic treatments are only allowed under restricted conditions.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The physical and chemical behaviour of soils is controlled in part by the amounts of mineral particles of
different sizes in the soil. The subject of this document is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral soil), within stated size classes.
The determination of particle size distribution is affected by organic matter, soluble salts, cementing agents
(such as iron compounds), relatively insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree, upon drying, that the particle size distribution of
the dried material bears little or no relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those developed from recent volcanic
[4]
deposits, some highly weathered tropical soils, and soils often described as “cohesive” (see Reference [4]).).
Other soils, such as the so-called “sub-plastic” soils of Australia, show little or no tendency to disperse under
normal laboratory treatments, despite field evidence of large clay content.
The procedures given in this document recognize these kinds of differences between soils from different
environments, and the methodology presented is designed to deal with them in a structured manner. Such
differences in soil behaviour can be very important, but awareness of them depends usually on local
knowledge. Given that the laboratory is commonly distant from the site of the field operation, the information
supplied by field teams becomes crucial to the choice of an appropriate laboratory procedure. This choice can
be made only if the laboratory is made fully aware of this background information.
v
FINAL DRAFT International Standard ISO/FDIS 11277:2026(en)

Soil quality — Determination of particle size distribution in mineral
soil material — Method by sieving and sedimentation
WARNING — Persons using this document should be familiar with usual laboratory practice. This
document does not purport to address all safety problems, if any, associated with its use. It is the
responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — — Tests, conducted in accordance with this document, shall be carried out by suitably
qualitfiedtrained staff.
1 Scope
This document specifies a basic method of determining the particle size distribution applicable to a wide range
of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with
the less common soils mentioned in the introduction. This document has been developed largely for use in the
field of environmental science, and its use in geotechnical investigations is something for which professional
advice might be required.
A major objective of this document is the determination of enough size fractions to enable the construction of
a reliable particle-size-distribution curve.
This document does not apply to the determination of the particle size distribution of the organic components
of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It is also realized that
the chemical pre-treatments and mechanical handling stages in this document could cause disintegration of
weakly cohesive particles that, from field inspection, might be regarded as primary particles, even though such
primary particles could be better described as aggregates. If such disintegration is undesirable, then this
document is not used for the determination of the particle size distribution of such weakly cohesive materials.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ISO 11265, Soil quality Environmental solid matrices — Determination of the specific electrical conductivity
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
ISO 3310--1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310--2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1
3.1 Diameter
diameter of a particle
diameter of a sphere whose behaviour in suspension matches that of the particle
4 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as given
below used in this document.
C specific heat of the liquid (4,18 J/g·K for water)
P
d equivalent spherical diameter of the particle of interest mm
p
2 2
g acceleration due to gravity (981 cm/s ) cm/s
γ Electricalelectrical conductivity mS/m
c
h height of the bulb mm
H length from the neck of the bulb to graduation d mm
L distance between the graduation marks on the measuring cylinder mm
L’ observed hydrometer reading
m mass of solid material in 500 ml of dispersant solution g
d
m mass of residue g
r
m Samplesample mass g
t
m mass of solid in suspension in 500 ml g
fx
m mass of material from the xth pipette sampling g
sx
M mass of liquid (g) g
η dynamic viscosity of water at the test temperature (as shown in Table B.2Table B.2)) mPmPa/s
P proportion
P delivered acoustic power
ac
P proportion of material <2 mm in the total soil
s
P proportion of the fraction <2 mm
t
P Proportionproportion in total soil mass
tsm
P Proportionproportion retained on the 6,3 mm sieve
6,3
P Proportionproportion retained on the 16 mm sieve
P Proportionproportion retained on the 20 mm sieve
p delivered acoustic power
ac
3 3
ρ mean particle density (2,65 Mg/m , see the note in Clause 4Clause 4);); Mg/m
s
3 3
ρ density of the suspension liquid (1,00 Mg/m , see the note in Clause 4Clause 4);); Mg/m
w
t elapsed time s
Δt time s
ΔT temperature K
V Calibratedcalibrated volume of the pipette ml
c
V volume of the hydrometer bulb ml
h
V indicated volume of the measuring cylinder between the graduations used in the ml
L
determination of L
z effective depth at which the density of the suspension is measured mm
z meniscus correction
m
5 Principle
The particle size distribution is determined by a combination of sieving and sedimentation, starting from air-
dried soil (see Reference 4[4]).). A method for undried soil is given in Annex AAnnex A. Particles not passing
a 2 mm aperture sieve are determined by dry sieving. Particles passing a 2 mm aperture sieve, but retained
on a 0,063 mm aperture sieve, are determined by a combination of wet and dry sieving, whilst particles.
Particles passing a 0,063 mm aperture sieve are determined by sedimentation.
Note NOTE 1 The test sieves are specified as typtype of metal wire cloth.
The pipette method is preferred. As an alternative, the hydrometer method is given in Annex BAnnex B. A
combination of sieving and sedimentation enables the construction of a continuous particle-size-distribution
curve.
The key points in this procedure are summarized as a flow chart in Figure 2Figure 2. This document requires
that the proportions of fractions separated by sedimentation and sieving be determined from the masses of
such fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such
things as the interaction of particles with electromagnetic radiation or electrical fields (see Reference 2[2]).).
There are often considerable difficulties in relating the values obtained by these different methods for the
same sample. It is one of the intentions of this document that close adherence to its details should help
minimize interlaboratory variation in the determination of the particle size distribution of mineral soils.
Therefore, the proportions of fractions shall be determined only by weighing. If this is not the method used,
then conformance with this document cannot be claimed in the test report (see Clause 10Clause 10).).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder
is in accordance with Stokes'sStokes’s Law (see References [2], [4[2], [4]] and [7[7]),]), and the constraints
that this implies, namely:
a) a) the particles are rigid, smooth spheres;
b) b) the particles settle in laminar flow, i.e. the Reynolds Numbernumber is less than
aboutapproximately 0,2; this constraint sets an upper equivalent spherical particle diameter (see below)
[2]
slightly greater than 0,06 mm for Stokesian settling under gravity (Reference [2]););
c) c) the suspension of particles is sufficiently dilutediluted to ensure that no particle interferes with
the settling of any other particle;
d) d) there is no interaction between the particle and fluid;
e) e) the diameter of the suspension column is large compared to the diameter of the particle, i.e.
the fluid is of “infinite extent”;
f) f) the particle has reached its terminal velocity;
g) g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of equivalent spherical diameter. It is the principle upon which
the expression of the diameter of particles, as derived from sedimentation, is based in this document.
Stokes'sStokes’s Law can be written, for the purposes of this document, as in Formula (1)Formula (1)::
(1)
𝑡𝑡 = 18𝜂𝜂ℎ/[(𝜌𝜌 −𝜌𝜌 )𝑔𝑔𝑑𝑑 ] (1)
𝑠𝑠 w p
NOTE 2 It is realized that there are considerable differences between the densities of soil particles, but for the
purposes of this document it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m
[8] 3
(Reference [8]),), as this is the commonest mineral in a very wide range of soils. The density of water is 0,998 2 Mg/m
3 [6]
and 0,995 6 Mg/m at 20 °C and 30 °C, respectively (see Reference [6]).). Given the effect of the addition of a small
amount of dispersant (see 9.3.29.3.2),), the density of water is taken as 1,000 0 Mg/m over the permitted temperature
range of this document (see 9.2.29.2.2).).
Furthermore, for routine use, it is recommended that the sampling times be converted to minutes or hours, or
both, as appropriate, to lessen the risk of error (see Table 3Table 3).).
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand, silt,
etc. The meaning of such trivial names differs between countries, and in some cases, there are no exact
translations of such words from one language to another; for example, the Dutch word “zavel” has no
equivalent in English. The only fraction for which there appears to be common agreement is clay, which is
[4]
defined as material of less than 0,002 mm equivalent spherical diameter (References [4]).). Such trivial
names shall not be used in describing the results of particle size determination according to this document.
Phrases such as “. passing a 20 mm aperture sieve .” or “. less than 0,063 mm equivalent spherical diameter
...” shall be used instead. If trivial names shall beare used, for example, to cross-reference to another
International or National Standard, then the trivial name should be defined explicitly, to remove any doubt as
to the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent spherical diameter) (see
Clause 4Clause 4).). Furthermore, it is common to use the word “texture” to describe the results of particle-
size-distribution measurements, e.g. “the particle size of this soil is of clay texture”. This is incorrect as the two
concepts are different, and the word “texture” shall not be used in the test report (see Clause 10Clause 10)) to
describe the results obtained using this document.
6 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1Table 1 gives recommended minimum
masses.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming >10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
Maximum size of material forming >10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
20 2
14 1
10 0,5
6,3 0,5
5 0,2
2 or smaller 0,1
7 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm
aperture sieve. In this case, the test sample (9.5(9.5)) can be taken either according to the procedures in ISO 11464 or
from the material passing a 2 mm aperture sieve according to 8.28.2.
8 Dry sieving (material >2 mm)
8.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2Table 2
gives the maximum mass which shall be retained on sieves of different diameters and apertures. If more than
this amount of material is retained, then it shall be subdivided appropriately and sieved again.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as
the sieve aperture, and the relationship between the various numbers is not immediately obvious. The use of
mesh numbers as a measurement of particle size is difficult to justify and shall not be used in reporting the
results of the procedures described in this document.
8.2 Apparatus
8.2.1 8.2.1 Test sieves, with apertures according to ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (see Table 1Table 1 and
8.2.39.2.3).). The apertures chosen shall be stated in the test report (Clause 10(Clause 10).). The accuracy of
the sieves shall be verified monthly against a set of master sieves kept for this purpose, using an accepted
[2]
method such as particle reference materials, microscopy, etc. (see Reference [2])) depending on the sieve
aperture. Tolerances shall meet the requirements of ISO 3310--1 and ISO 3310--2. Sieves that do not meet
these specifications shall be discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended for
the larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly
when in regular use, and on every occasion if used less often. A record shall be kept of such inspections. Round-
hole sieves shall not be used.
8.2.2 8.2.2 Balance, capable of weighing to an accuracy of within ±0,5 g.
8.2.3 8.2.3 Mechanical sieve shaker.
It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very
heavy-duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller
apertures.
8.2.4 8.2.4 A sieve brush and a stiff brush.
8.2.5 8.2.5 Ultrasonic bath, able to provide an acoustic power P p (W) level in the range of 5 W to 20 W
ac ac
per litre of water (see Annex DAnnex D),), typically operating at a frequency between 37 kHz to 45 kHz.
8.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the
weighed material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the
stiff brush (to remove any adhering soil), sieve the material. Take care not to detach any fragments from the
primary particles. Sieve the retained material on the nest of sieves of selected apertures (8.2.1(8.2.1)) and
record the amount retained on each sieve to the nearest 0,5 g. Do not overload the sieves (see Table 1Table 1))
but sieve the material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (see
2 3
Table 2Table 2)) obtained by an appropriate subsampling method (see Clause 6Clause 6),), and place this on
a nest of sieves, the lowermost having an aperture of 2 mm. Shake the sieves mechanically until no further
material passes any of the sieves (see Note). Record the mass of material retained on each sieve and the mass
passing the 2 mm aperture sieve.
The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for
2 3
sieve damage and discard sieves as appropriate (see 8.2.18.2.1). ). For practical purposes, a
standard sieve shaking time should be chosen which gives an acceptable degree of sieving efficiency with a
wide range of soil materials.
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Test sieve Maximum mass
aperture
kg
Sieve diameter
mm
mm 450 400 300 200 100
50 10 8,9 4,5 — —
37,5 8 7,1 3,5 — —
28 6 5,3 2,5 — —
20 4 3,6 2 — —
14 3 2,7 1,5 — —
10 2 1,8 1 — —
6,3 1,5 1,3 0,75 — —
5 1 0,9 0,5 — —
3,35 — — — 0,3 0,15
2 — — — 0,2 0,1
1,18 — — — 0,1 0,05
0,6 — — — 0,075 0,037 5
Test sieve Maximum mass
aperture
kg
Sieve diameter
mm
mm 450 400 300 200 100
0,425 — — — 0,075 0,037 5
0,3 — — — 0,05 0,025
0,212 — — — 0,05 0,025
0,15 — — — 0,04 0,02
0,063 — — — 0,025 0,012 5
8.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained
by each sieve as a proportion of m . For example, as in Formula (2) (Formula (2))::
𝑃𝑃 = [𝑚𝑚(20 mm)]/𝑚𝑚 (2)
20 1
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by m /m and
2 3
calculate this as a proportion of m . For example, as in Formula (3) (Formula (3))::
(3)
⁄ ⁄
𝑃𝑃 =𝑚𝑚(6,3 mm)[(𝑚𝑚 𝑚𝑚 ) 𝑚𝑚 ]
6,3 2 3 1
(3)
Present the results as a Table showing, to two significant figures, the proportion by mass retained on each
sieve and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative
distribution curve (see Figure 1Figure 1).).
9 Wet sieving and sedimentation (material <2 mm)
9.1 General
This clause specifies the procedure (see Figure 2Figure 2)) for the determination of the particle size
distribution of the material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical
diameter (see noteNOTE). In order to ensure that primary particles, rather than loosely bonded aggregates,
are measured, organic matter and salts are removed, especially sparingly soluble salts such as gypsum which
would otherwise prevent either dispersion or promote flocculation of the finer soil particles in suspension, or
both (see 9.69.6),), and a dispersing agent is added (9.3.2(9.3.2).). These procedures are required in this
document, and their omission shall invalidate its application. Sometimes iron oxides and carbonates,
especially of calcium and/or magnesium, are also removed. Preferred procedures for the removal of these
compounds are given in the notes in 9.79.7, 9.8, 9.8 and 9.99.9. The removal of any compound shall be
recorded in the test report (see Clause 10Clause 10).).
NOTE Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent spherical
diameter. However, the method cannot be used to divide this class further with reliability, as particles less than
aboutapproximately 0,001 mm equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian
[2]
motion (see Reference [2]).).
9.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in
[7]
batches. Experience has shown (see Reference [7])) that one operator can process up to 36 samples in a
batch at a time, given sufficient apparatus and space, especially if calculations are dealt with by a computer.
9.2.1 9.2.1 Sampling pipette or sampling needle, of a pattern similar to that shown in Figure 3Figure 3
with sideways openings, the chief requirement being that the. The smallest practicable horizontal zone of
sedimenting suspension shall be sampled. The pipette shall be of not less than 10 ml volume and shall be held
in a frame so that it can be lowered to a fixed depth within a sedimentation tube (see Figure 4Figure 4).).
NOTE 1 Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes.
A 25 ml volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be sufficient
for soils with down to approximately 10 % mass fraction of <0,063 mm equivalent spherical diameter. Below this amount,
greater precision is likely to be obtained with a pipette of larger volume.
NOTE 2 The position of the pipette is adjusted to the new suspension surface after each sampling.
NOTE 3 Automated systems can be used, if the results are proven to be equivalent.
Figure 1 — Particle-size-distribution chart
Figure 2 — Flow chart of the soil sample pretrement procedure to determine
particle size of mineral soil
Dimensions in millimetres
Key
1 bulb (capacity: approximately 125 ml)
2 pipette and changeover cock (capacity at least 10 ml)
3 sideways opening
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 3 — Sampling pipette for sedimentation test
Key
1 bulb (capacity: approximately 125 ml)
2 pipette and changeover cock (capacity at least 10 ml)
3 sideways opening
1 and 2 125 ml bulb funnel with stopcock
3 safety-bulb suction inlet tube
4 safety bulb
5 tap
6 outlet tube
7 sampling pipette
8 sedimentation tube
9 scale graduated in millimetres
10 clamps
11 sliding panel
12 constant-temperature bath
a
4, 6 and 7 are joined to three-way stopcock 5.
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 3 — Sampling pipette for sedimentation test
Key
1 and 2 125 ml bulb funnel with stopcock 8 sedimentation tube
3 safety-bulb suction inlet tube 9 scale graduated in millimetres
4 safety bulb 10 clamps
5 tap 11 sliding panel
6 outlet tube 12 constant-temperature bath
7 sampling pipette
a
4, 6 and 7 are joined to three-way stopcock 5.
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
9.2.2 9.2.2 Constant-temperature room or bath, which can be maintained at between 20 °C and
(30 ± 1) °C. If a bath is used, it shall accept a sedimentation tube immersed to the 500 ml or 1 000 ml mark and
shall not vibrate the contents of the tube. Similarly, if a room is used, it, and its furniture, shall be constructed
so that activity does not cause the tubes and their contents to vibrate.
NOTE This temperature range has been chosen to allow for the difficulties of maintaining one specified temperature
in different parts of the world. In addition, the lower temperature gives sedimentation times that fit well into an average
working day, whilst the upper temperature still allows for a sensible settling time for the fraction 0,063 mm equivalent
spherical diameter (see Clause 4Clause 4 and Table 3Table 3).).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m ) at a sampling depth
p
from the surface of (100 ± 1) mm at different temperatures assuming a particle density of
3 3
and density of water with dispersant of 1,00 Mg/m
2,65 Mg/m
Times, after mixing, of starting sampling operation
st a nd rd th
T η 1 sample 2 sample 3 sample 4 sample
°C mPa/s min s min s min s h min s
15 1,139 1 4 5 17 53 11 8 47 45
16 1,109 1 2 5 8 51 47 8 33 51
17 1,081 1 1 5 1 50 29 8 20 53
18 1,053 0 59 4 53 49 10 8 7 54
19 1,027 0 58 4 46 47 57 7 55 52
20 1,002 0 56 4 38 46 46 7 44 5
21 0,978 0 55 4 32 45 39 7 32 55
22 0,955 0 53 4 25 44 34 7 22 16
23 0,933 0 52 4 19 43 33 7 12 4
24 0,911 0 51 4 13 42 32 7 1 58
25 0,891 0 50 4 8 41 35 6 52 37
26 0,871 0 49 4 2 40 39 6 43 21
27 0,851 0 48 3 56 39 43 6 34 5
28 0,833 0 47 3 51 38 53 6 25 44
29 0,815 0 46 3 46 38 2 6 17 24
30 0,798 0 45 3 42 37 14 6 9 31
31 1,781 0 44 3 37 36 27 6 1 39
32 0,764 0 43 3 33 35 42 5 54 11
33 0,749 0 42 3 28 34 58 5 46 57
34 0,734 0 41 3 24 34 16 5 39 58
35 0,719 0 40 3 20 33 35 5 33 12
d (mm) 0,063 0,02 0,006 3 0,002
p
Sampling depth (m) 0,2 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1
a Sampling depth (200 ± 1) mm to allow adequate time for the stabilization of the suspension after mixing.
9.2.3 9.2.3 Glass sedimentation tubes, without pouring lips, of internal diameter approximately
50 mm to 60 mm, and overall length of approximately 350 mm to 450 mm, graduated at 500 ml or 1 000 ml
volume, and with either rubber bungs to fit or a stirrer.
9.2.4 9.2.4 Stirrer, of non-corrodible material.
9.2.5 9.2.5 Weighing vessels, inert material, with masses known to the nearest 0,000 1 g.
9.2.6 9.2.6 Mechanical shaker, capable of keeping 30 g of soil in suspension in 150 ml of liquid.
NOTE For keeping the soil in suspension, a suitable device could be an end-to-end type of shaker [e.g. (10 to
30) revolutions/min] or a stirrer.
9.2.7 9.2.7 Test sieves, conforming with ISO 565, ISO 3310--1 and ISO 3310--2, having apertures of 2 mm
and 0,063 mm, plus two intermediate sieves. The test report shall state which apertures are used. Round-hole
sieves shall not be used.
NOTE The choice of the sieve of aperture 0,063 mm given here is for illustration but accords with the widespread
use of this particle size to define the upper boundary of the silt fraction. Local requirements can specify another aperture.
The choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests that sieves
of aperture close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
9.2.8 9.2.8 Suitable sample dividersampledivider (see Clause 6Clause 6).).
9.2.9 9.2.9 Balance, capable of weighing to an accuracy of within ±0,000 1 g.
9.2.10 9.2.10 Drying oven, capable of maintaining a temperature between 105 °C and 110 °C.
9.2.11 9.2.11 Stop clock, readable to 1 s.
9.2.12 9.2.12 Desiccator, containing anhydrous silica gel (preferably of the self-indicating type), capable of
holding the five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and
110 °C when it is no longer effective.
9.2.13 9.2.13 Glass beaker, of capacity 650 ml with a cover glass to fit, or a 300 to 500 ml centrifuge bottle
with a leak proof cap.
NOTE This apparatus is used for chemical pre-treatment during which a constant problem is the adhesion of very
fine particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone
centrifuge bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide and
common dispersing agents. Their use can also save significant amounts of operator time.
9.2.14 9.2.14 Centrifuge, capable of holding the 300 ml to 500 ml centrifuge bottles (see 9.2.139.2.13).).
9.2.15 9.2.15 Measuring cylinder, of capacity 1 000 ml.
9.2.16 9.2.16 Pipette, of capacity between 10 ml to 50 ml (25 ml recommended) (see 8.2.18.2.1).).
9.2.17 9.2.17 Glass filter funnel, capable of holding the 0,063 mm sieve.
9.2.18 9.2.18 Wash bottle containing water (see 8.38.3).).
9.2.19 9.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a
rubber sleeve at one end.
9.2.20 9.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C or water
bath, capable of maintaining a temperature between 90 °C and 95 °C. A hotplate is essential if polymer
centrifuge bottles are used for the chemical pretreatment, but a Bunsen burner, gauze and tripod are sufficient
if glass beakers are used.
9.2.21 9.2.21 Suction device, similar to that shown in Figure 5Figure 5 is useful, but not essential.

Key
1 flexible tube
2 pasteur pipette or similar
3 reservoir (5 l or 10 l)
a
To vacuum.
Figure 1 flexible tube
2 pasteur pipette or similar
3 reservoir (5 l or 10 l)
a
To vacuum.
Figure 5 — Suction device
9.2.22 9.2.22 Sieve brush.
9.2.23 9.2.23 Electrical conductivity meter, accurate to 1 mS/m.
9.3 Reagents
All reagents shall be of recognized analytical grade. Use water having an electrical conductivity no greater than
10 mS/m at 25 °C at the time of use.
9.3.1 9.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE A 30 % volume fraction solution is one which yields 30 ml of gaseous oxygen from 100 ml of solution (under
standard conditions of temperature and pressure) upon reduction to water, either by chemical means or by boiling.
9.3.2 9.3.2 Solution of a dispersing agent.
As a dispersing agent, dissolve 33 g of sodium hexametaphosphate and 7 g of anhydrous sodium carbonate in
water to make 1 l of solution. Store away from strong sunlight and preferably in a dark bottle. Record the date
of preparation on the bottle. The solution is unstable and shall be replaced after one month.
Another suitable dispersant is 0,1 M sodium pyrophosphate solution (tetrasodiumdiphosphate decahydrate
Na P O · 10 H O).
4 2 7 2
The sodium carbonate buffers the solution and the suspension of the soil, to approximately pH 9,8. The
described dispersing agents have been found successful with a very wide range of soils. However, if there are
signs that dispersion is ineffective, consider firstly that flocculating salts might be present (see 9.79.7).). If
dispersion is still unsuccessful after removal of salts, then other dispersing agents should be considered. A
very effective but less widely used dispersing agent is prepared by replacing the sodium carbonate with 20 %
volume fraction ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the hexametaphosphate
[3]
solution. There are many other dispersing agents (see Reference [3]).). Whichever is chosen, considerable
investigation will be required to establish its effectiveness. It is noticed that some soils show fewer problems
of dispersion if analysed without drying (see Annex AAnnex A).). Some soils derived from recent volcanic
[10]
deposits will disperse more effectively in an acid medium (see Reference [10]).).
9.3.3 9.3.3 Octan-2-ol, or a similar volatile antifoaming agent.
NOTE Octan-2-ol is highly effective and relatively long-lasting. Ethanol or methanol can also be used,
but the use of pentan-2-ol (amyl alcohol) is discouraged because it is potentially addictive.
9.4 Calibrations
9.4.1 Sampling pipette
Clean and dry the pipette (see Figure 4Figure 4)) thoroughly and immerse the tip in water held at the same
temperature as that of the constant-temperature environment (9.2.2(9.2.2).). By means of a tube attached to
the safety-bulb suction inlet tube (item 3 in Figure 4C,), draw water into the pipette above the tap (item 5 in
Figure 4E.). Drain off the water above Ethe tap through the outlet tube (item 6 in Figure 4F.). Drain the pipette
into a weighing vessel (9.2.5(9.2.5)) of known mass and determine the new mass. From the known masses,
calculate by use of the density the internal volume of the pipette. Repeat this exercise three times and take the
average of the three volumes as the internal volume of the pipette to the nearest 0,05 ml (V ml).
c
...