oSIST prEN ISO 3675:2026

• Status: Not Published
• Public Enquiry End Date: 22-Sep-2026
• ICS: 75.040 - Crude petroleum
• ICS: 75.080 - Petroleum products in general
• Technical Committee: NAD - Petroleum products, lubricants and related products
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 01-Jul-2026
• Due Date: 18-Nov-2026
• Ref Project: prEN ISO 3675 - Crude petroleum and liquid petroleum products - Laboratory determination of density - Hydrometer method (ISO/DIS 3675:2026)

• Revises: SIST EN ISO 3675:1999 - Crude petroleum and liquid petroleum products - Laboratory determination of density - Hydrometer method (ISO 3675:1998)
• Effective Date: 01-Sep-2026

Overview

oSIST prEN ISO 3675:2026:2026, "Crude petroleum and liquid petroleum products - Laboratory determination of density - Hydrometer method," is a draft European and International Standard developed by CEN and ISO. This standard specifies the hydrometer method for laboratory measurement of density in crude oil, refined petroleum products, and related liquid hydrocarbons. Accurate determination of density is crucial for quality control, regulatory compliance, and commercial transactions in the petroleum industry.

Key Topics

• Scope and Relevance: The standard applies to crude petroleum, liquid petroleum products, and mixtures with a Reid vapour pressure up to 100 kPa. It addresses both mobile transparent liquids and viscous or opaque products by providing precise procedural adaptations.
• Hydrometer Method: The procedure utilizes glass hydrometers, compliant with ISO 387, to measure density at a controlled temperature. The standard emphasizes sample handling, proper temperature control, and meniscus reading for different liquid types.
• Apparatus and Equipment: Specifications cover hydrometer cylinders, hydrometers, constant temperature baths, thermometers, and optional stirring rods. The standard also allows for resistance thermometers when measurement accuracy matches glass thermometers.
• Sample Preparation: Outlines protocols for mixing and heating samples, especially volatile and waxy products, to maintain representativeness and minimize loss of light components.
• Measurement Procedure: Detailed, stepwise guidance ensures sample homogeneity, proper hydrometer immersion, and meniscus reading, with corrections for temperature and meniscus as necessary.
• Precision and Reporting: Provides repeatability and reproducibility data, clarifying expected measurement variation between operators and labs. The final density result is to be reported at a stated temperature per clear instructions.

Applications

The hydrometer method outlined in oSIST prEN ISO 3675:2026:2026 is vital for:

• Quality Control in Refineries and Terminals: Regular density measurements ensure product consistency and specification compliance.
• Commercial Transactions: Density is a key parameter in volumetric-to-mass conversions and helps set pricing or trading terms for crude oil and finished products.
• Regulatory and Customs Declarations: Accurate density data supports tax, reporting, and regulatory submissions.
• Research and Product Development: Laboratories use standardized density measurements to compare formulations, monitor handling properties, and study the impact of blending or additives.
• Operational Efficiency: Onsite and laboratory petroleum testing enables prompt decision-making about storage, blending, or transportation operations.
• Sampling Protocols: Proper sample preparation ensures representativeness, critical for reliable test results, especially for products affected by wax or volatility.

Related Standards

• ISO 91: Petroleum and related products - Temperature and pressure volume correction factors
• ISO 387: Hydrometers - Principles of construction and adjustment
• ISO 3170: Hydrocarbon Liquids - Manual sampling
• ISO 3171: Petroleum liquids - Automatic pipeline sampling

Additional annexes in oSIST prEN ISO 3675:2026:2026 provide guidance on hydrometer construction, adjustment, and correction factors for readings at non-standard temperatures, ensuring measurement traceability and global alignment.

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Keywords: crude petroleum density determination, hydrometer method, laboratory testing, petroleum product measurement, oSIST prEN ISO 3675:2026:2026, oil sample preparation, refining quality control, petroleum industry standards, CEN ISO standards, hydrocarbon density testing.

SLOVENSKI STANDARD
01-september-2026
Surova nafta in tekoči naftni proizvodi - Laboratorijsko določanje gostote - Metoda
z areometrom (ISO/DIS 3675:2026)
Crude petroleum and liquid petroleum products - Laboratory determination of density -
Hydrometer method (ISO/DIS 3675:2026)
Rohöl und flüssige Mineralölerzeugnisse - Bestimmung der Dichte im Labor - Aräometer-
Verfahren (ISO/DIS 3675:2026)
Pétrole brut et produits pétroliers liquides - Détermination en laboratoire de la masse
volumique - Méthode à l'aréomètre (ISO/DIS 3675:2026)
Ta slovenski standard je istoveten z: prEN ISO 3675
ICS:
75.040 Surova nafta Crude petroleum
75.080 Naftni proizvodi na splošno Petroleum products in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 3675
ISO/TC 28/SC 2
Crude petroleum and liquid
Secretariat: BSI
petroleum products — Laboratory
Voting begins on:
determination of density —
2026-07-02
Hydrometer method
Voting terminates on:
2026-09-24
Pétrole brut et produits pétroliers liquides — Détermination en
laboratoire de la masse volumique — Méthode à l'aréomètre
ICS: 75.080; 75.040
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.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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 3675:2026(en)
DRAFT
ISO/DIS 3675:2026(en)
International
Standard
ISO/DIS 3675
ISO/TC 28/SC 2
Crude petroleum and liquid
Secretariat: BSI
petroleum products — Laboratory
Voting begins on:
determination of density —
Hydrometer method
Voting terminates on:
Pétrole brut et produits pétroliers liquides — Détermination en
laboratoire de la masse volumique — Méthode à l'aréomètre
ICS: 75.080; 75.040
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.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
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
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 3675:2026(en)
ii
ISO/DIS 3675:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and Definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sampling . 3
7 Sample preparation . 3
7.1 Sample mixing .3
7.1.1 Volatile crude oils and petroleum products having a RVP greater than 50 kPa .3
7.1.2 Waxy crude oils .3
7.1.3 Waxy distillates .4
7.1.4 Residual fuel oils . .4
7.2 Test temperature .4
8 Verification of apparatus . 4
9 Preparation of apparatus . 4
10 Procedure . 5
11 Calculation . 7
12 Expression of results . 8
13 Precision . 8
13.1 Repeatability .8
13.2 Reproducibility .8
14 Test report . 9
Annex A (normative) “Corrections to hydrometer readings for soda-lime glass hydrometers
where the hydrometers have been calibrated at a temperature other than the
temperature at which the density is to be reported.” .10
Annex B Principles of construction and adjustment of hydrometers .11
Bibliography .18

iii
ISO/DIS 3675:2026(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.
Draft International Standards adopted by the technical committees are circulated to the member bodies for
voting. Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
International Standard ISO 3675 was prepared by Technical Committee ISO/TC 28, Petroleum products and
lubricants, subcommittee SC 2, Static petroleum measurement.
This fifth edition cancels and replaces the fourth edition, of which it constitutes a Technical revision.
Annex A forms an integral part of this International Standard. Annex B is for information only. Appendix 1
has been added, since after the withdrawal of ISO649/1 “Laboratory glassware - Density hydrometers for
general purposes - Part 1 : Specification” in 2024, there is no remaining ISO standard covering the general
principles for the construction of hydrometers.

iv
DRAFT International Standard ISO/DIS 3675:2026(en)
Crude petroleum and liquid petroleum products —
Laboratory determination of density — Hydrometer method
WARNING — The use of this International Standard may involve hazardous materials, operations
and equipment. This International Standard does not purport to address all the safety problems
associated with its use. It is the responsibility of the user of this standard to establish appropriate
safety and health practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a method for the laboratory determination, using a glass hydrometer,
of the density of crude petroleum, liquid petroleum products, and mixtures of petroleum and non-petroleum
products normally handled as liquids and having a Reid vapour pressure (RVP) of 100 kPa or less.
This International Standard is suitable for determining the density of mobile transparent liquids. It can
also be used for viscous liquids by carrying out the determinations at temperatures above ambient using a
suitable liquid bath for temperature control. It can also be used for opaque liquids by reading the hydrometer
scale where the top of the meniscus meets the stem of the hydrometer and applying a correction from table 1
(see 11.2).
Since hydrometers are calibrated to read correctly at the specified temperature, scale readings made at
other temperatures are only hydrometer readings and not values of density at these other temperatures.
NOTES
1 The accuracy of the density, determined by the procedures given in this International Standard, for volatile and/
or waxy crude oils containing free and/or suspended water and sediments can be less than inferred from the
precision data quoted in clause 13. This is due to the possible loss of light components during sample mixing.
However, sample mixing is necessary to ensure that the test portion transferred to the hydrometer cylinder is
as representative as possible of the bulk sample. Suggested techniques are given in clause 7 which may help to
minimize such loss of light components.
2 Values of density at any temperature can be converted using standard measurement tables to equivalent values
of other units, such as API gravity or relative density, so that measurements may be made in the units of local
convenience.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute
provisions of this International Standard. The latest edition of the normative document referred to applies.
Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 91, Petroleum and related products — Temperature and pressure volume correction factors (petroleum
measurement tables) and standard reference conditions
ISO 387, Hydrometers — Principles of construction and adjustment
ISO 3170, Hydrocarbon Liquids — Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
3 Terms and Definitions
For the purposes of this International Standard, the following definitions apply.

ISO/DIS 3675:2026(en)
3.1
density
mass per unit volume expressed in either kilograms per cubic metre or grams per millilitre at a stated
temperature
3.2
cloud point
temperature at which a cloud of wax crystals first appears in a liquid when it is cooled under specified
conditions
3.3
wax appearance temperature
WAT
temperature at which waxy solids form when petroleum or petroleum products are cooled under specified
conditions
3.4
pour point
lowest temperature at which a sample of petroleum or petroleum product will continue to flow when it is
cooled under specified conditions
4 Principle
The sample is brought to a specified temperature and a test portion transferred to a hydrometer cylinder that
has been brought to approximately the same temperature. The appropriate hydrometer, whose temperature
has also been regulated, is lowered into the test portion and allowed to settle. After temperature equilibrium
has been reached, the hydrometer scale is read, and the temperature of the test portion taken. If necessary,
the hydrometer cylinder and its contents are placed in a constant temperature bath to avoid excessive
temperature variation during the test.
5 Apparatus
5.1 Hydrometer cylinder, of clear glass, or transparent plastics material, with an inside diameter at least
25 mm greater than the outside diameter of the hydrometer (5.2) and a height such that the hydrometer
floats in the test portion with at least 25 mm clearance between the bottom of the hydrometer and the
bottom of the cylinder.
Plastics material used for the construction of hydrometer cylinders shall be resistant to discolouration or
attack and shall not affect the properties of the material being tested. In addition, they shall not become
opaque under prolonged exposure to light.
NOTE For convenience in pouring, the hydrometer cylinder may have a lip on the rim.
5.2 Hydrometers, of glass, graduated in units of density, conforming to ISO 387 and the requirements
given in table 1. (See also annex A.) Choose a hydrometer which is suitably sized for the amount of sample
available, and has the required readability.
Table 1 — Requirements for hydrometers
Unit Density range Each unit Scale interval Maximum scale error Meniscus correction
Kg/m 600 to 1 100 20 0,2 ±0,2 ±0,3
600 to 1 100 50 0,5 ±0,3 ±0,7
600 to 1 100 50 1,0 ±0,6 ±1,4
g/ml 0,600 to 1,100 0,02 0,000 2 ±0,000 2 ±0,000 3
0,600 to 1,100 0,05 0,000 5 ±0,000 3 ±0,000 7
0,600 to 1,100 0,05 0,001 0 ±0,000 6 ±0,001 4

ISO/DIS 3675:2026(en)
5.3 Constant temperature bath, if required, of dimensions such that it can accommodate the hydrometer
cylinder with the test portion fully immersed below the surface of the bath liquid and a temperature control
system capable of maintaining the bath at the test temperature ±0,25 °C, throughout the duration of the test.
5.4 Thermometer, If glass, having a range, and maximum error, as shown in table 2.
Table 2 — Requirements for glass thermometers
Range Graduation interval Maximum scale error
°C
-1 to +38 0,1 ±0,1
-29 to +102 0,2 ±0,15
NOTES
1 Thermometers IP 39C and IP 64C/ASTM 12C are suitable. Glass thermometers containing mercury should only be
used if no other means of temperature measurement is available.
2 Resistance thermometers may be used, provided that the total uncertainty of the calibrated system is not greater
than the uncertainty when using liquid-in-glass thermometers.
5.5 Glass or plastic stirring rod, optional, approximately 450 mm in length.
6 Sampling
Samples shall be taken in accordance with ISO 3170, ISO 3171, or an equivalent National Standard.
NOTE When sampling volatile liquids using an automatic sampling technique, unless a sample receiver of variable
volume is used to collect the sample and transport it to the laboratory, loss of light components may occur which will
affect the accuracy of the density measurement.
7 Sample preparation
7.1 Sample mixing
The portion of the sample tested shall be as representative as possible of the bulk sample, and sample mixing
may be necessary. However, precautions shall be taken to maintain the integrity of the sample during this
operation.
The mixing of volatile crude oils and petroleum products containing sediments and/or water, or the heating
of waxy volatile crude oils or petroleum products may result in the loss of light components. Guidance as to
how to treat the different materials and to minimize such light component loss is given in 7.1.1 to 7.1.4.
7.1.1 Volatile crude oils and petroleum products having a RVP greater than 50 kPa
Mix the sample wherever possible in the original container, and in a closed system in order to minimize the
loss of light components.
NOTE Mixing volatile samples in open containers will lead to loss of light components and will affect the value of
the density obtained.
7.1.2 Waxy crude oils
If the crude oil has a pour point above 10 °C, or a cloud point or WAT (3.3) above 15 °C, warm the sample
to 9 °C above its pour point, or 3 °C above its cloud point or WAT, prior to mixing. Mix the sample wherever
possible in the original container, and in a closed system in order to minimize the loss of light components.

ISO/DIS 3675:2026(en)
7.1.3 Waxy distillates
Warm the sample to 3 °C above its cloud point or WAT prior to mixing.
7.1.4 Residual fuel oils
Heat the sample to the test temperature prior to mixing (see 7.2.1 and note 2 in 7.2.1).
7.2 Test temperature
7.2.1 Bring the sample to the test temperature which shall be such that the sample is sufficiently fluid,
but not so high as to cause loss of light components, nor so low as to result in the presence of wax in the test
sample.
NOTES
1 The density determined by the hydrometer method is most accurate at or near the temperature at which the
hydrometer was calibrated.
2 The hydrometer reading is obtained at a temperature appropriate to the physio-chemical characteristics of the
material being tested. This temperature is preferably close to the temperature at which the hydrometer was
calibrated or, when the density is used in conjunction with bulk oil measurements, close to ±3 °C, or at the bulk oil
temperature, to minimize errors due to volume correction.
7.2.2 For crude oil, bring the sample to 9 °C above its pour point, or 3 °C above its cloud point or wax
appearance temperature, whichever is the higher.
NOTE For crude oil, an indication of the wax appearance temperature can be found using IP 389 (see [4] in
annex B) with the modification of using 50 μl ± 0,5 μl of sample. The precision for determining WAT of crude oils using
IP 389 has not been determined.
8 Verification of apparatus
8.1 Hydrometers shall be regularly verified by comparison with a reference hydrometer traceable to a
National Standard or by calibration by hydrostatic weighing in a traceable density standard, and where
necessary recalibrated at least every five years. The frequency of recalibration should be determined by
the user, based on previous calibrations of this hydrometer, the temperature(s) at which it is used, and the
importance of the results to the end-user or client.
8.2 Thermometers shall be regularly verified by comparison with a reference thermometer traceable to a
National Standard.
9 Preparation of apparatus
9.1 Health & Safety legislation has caused a change in the material that is used to weight a hydrometer
during its manufacture. Lead shot is now rarely used, and steel is most common. Because such hydrometers
may be affected by the earth’s magnetic field, the highest precision hydrometers should be weighted with
zinc or other non-magnetic material. Care should be taken when choosing a hydrometer for high precision
work. The magnetic susceptibility of a hydrometer can be checked by passing a compass close to the
hydrometer bulb, and seeing whether the compass needle moves.
9.2 Check that the hydrometer scale is correctly located within the hydrometer stem by reference to the
datum mark. If the scale seems to have moved, reject the hydrometer. If a datum mark is not present, gently
tap the hydrometer on a bench, to check that the scale does not move.
9.3 Bring the hydrometer cylinder and hydrometer to approximately the sample temperature (see 7.2.1).

ISO/DIS 3675:2026(en)
10 Procedure
10.1 Transfer a portion of the sample at test temperature to the clean hydrometer cylinder at a stabilised
temperature, without splashing, avoiding the entrainment of air bubbles, and reducing to a minimum the
evaporation of the lower boiling constituents of volatile materials.
10.2 Remove any bubbles that have collected on the surface of the sample, by touching them with a piece of
clean filter paper.
10.3 Place the cylinder containing the sample in a vertical position in a location free from air currents and
where the temperature of the surrounding medium will not change by more than 2 °C during the time taken
to carry out the test. When testing at temperatures differing by more than ±2 °C from ambient, a constant-
temperature bath (5.3) shall be used to avoid excessive temperature changes (see 10.13).
10.4 Stir the test portion with the appropriate thermometer (see table 2), or, if using a resistance
thermometer, with a stirring rod (5.5), using a combination of vertical and rotational motions, to ensure
uniform temperature and density throughout the cylinder. Record the temperature to the nearest 0,1 °C.
Remove the thermometer, and if used the stirring rod, from the hydrometer cylinder.
10.5 Lower the appropriate hydrometer (5.2) into the liquid and release it when in
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