FprEN ISO 4787

Laboratory glass and plastic ware - Volumetric instruments - Methods for testing of capacity and for use (ISO/FDIS 4787:2021)

Laborgeräte aus Glas und Kunststoff - Volumenmessgeräte - Prüfverfahren und Anwendung (ISO/FDIS 4787:2021)

Dieses Dokument legt Verfahren für die Prüfung, Kalibrierung und Anwendung von Volumenmessgeräten aus Glas und Kunststoff fest, um eine größtmögliche Genauigkeit bei der Anwendung zu erhalten.
ANMERKUNG Als Prüfung wird der Vorgang bezeichnet, anhand dessen die Konformität des einzelnen Volumen-messgeräts mit der zutreffenden Norm untersucht wird; mit dem Ziel, eine Messabweichung an einem oder mehreren Punkten zu ermitteln.
Dieses Dokument gilt für Volumenmessgeräte mit Nennvolumen im Bereich von 100 μl bis 10 000 ml. Sie gelten für Vollpipetten (siehe ISO 648), für Messpipetten und Verdünnungspipetten (siehe ISO 835), für Büretten (siehe ISO 385), für Messkolben (siehe ISO 1042) und für Messzylinder (siehe ISO 4788 und ISO 6706).
Die Verfahren sind nicht für die Prüfung von Volumenmessgeräten mit Nennvolumen von weniger als 100 μl vorgesehen, z. B. für Mikroglasgeräte.
Dieses Dokument behandelt nicht ausdrücklich Pyknometer nach ISO 3507. Jedoch können die hier festgelegten Verfahren für die Volumenbestimmung zum größten Teil auch für die Volumenbestimmung von Pyknometern angewendet werden. Bei einigen Typen von Pyknometern kann eine besondere Handhabung erforderlich sein.

Verrerie et matériel en plastique de laboratoire - Instruments volumétriques - Méthodes d'essai de la capacité et d'utilisation (ISO/FDIS 4787:2021)

Laboratorijska oprema iz stekla in plastike - Instrumenti za volumetrična merjenja - Metode za preskušanje zmogljivosti in uporaba (ISO/DIS 4787:2021)

General Information

• Status: Not Published
• ICS: 17.060 - Measurement of volume, mass, density, viscosity
• ICS: 71.040.20 - Laboratory ware and related apparatus
• Technical Committee: CEN/TC 332 - Laboratory equipment
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Due Date: 20-Nov-2021
• Completion Date: 20-Nov-2021
• Ref Project: oSIST kprEN ISO 4787:2021 - Laboratory glass and plastic ware - Volumetric instruments - Methods for testing of capacity and for use (ISO/DIS 4787:2021)

RELATIONS

• Revised: EN ISO 4787:2011 - Laboratory glassware - Volumetric instruments - Methods for testing of capacity and for use (ISO 4787:2010, Corrected version 2010-06-15)
• Effective Date: 02-Sep-2020

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN ISO 4787:2021
01-marec-2021

Laboratorijska oprema iz stekla in plastike - Instrumenti za volumetrična merjenja -

Metode za preskušanje zmogljivosti in uporaba (ISO/DIS 4787:2021)

Laboratory glass and plastic ware - Volumetric instruments - Methods for testing of

capacity and for use (ISO/DIS 4787:2021)

Laborgeräte aus Glas und Kunststoff - Volumenmessgeräte - Prüfverfahren für Volumen

und Anwendung (ISO/DIS 4787:2021)

Verrerie et matériel en plastique de laboratoire - Instruments volumétriques - Méthodes

d'essai de la capacité et d'utilisation (ISO/DIS 4787:2021)
Ta slovenski standard je istoveten z: prEN ISO 4787
ICS:
17.060 Merjenje prostornine, mase, Measurement of volume,
gostote, viskoznosti mass, density, viscosity
71.040.20 Laboratorijska posoda in Laboratory ware and related
aparati apparatus
oSIST prEN ISO 4787:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 4787:2021
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oSIST prEN ISO 4787:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 4787
ISO/TC 48 Secretariat: DIN
Voting begins on: Voting terminates on:
2021-01-22 2021-04-16
Laboratory glass and plastic ware — Volumetric
instruments — Methods for testing of capacity and for use
ICS: 17.060; 17.060
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT 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
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 4787:2021(E)
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. ISO 2021
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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Summary of method .......................................................................................................................................................................................... 2

5 Volume and reference temperature ................................................................................................................................................. 2

5.1 Unit of volume ......................................................................................................................................................................................... 2

5.2 Reference temperature .................................................................................................................................................................... 2

6 Apparatus and calibration liquid ........................................................................................................................................................ 2

7 Factors affecting the accuracy of volumetric instruments ........................................................................................ 3

7.1 General ........................................................................................................................................................................................................... 3

7.2 Temperature .............................................................................................................................................................................................. 3

7.2.1 Temperature of the volumetric instrument .............................................................................................. 3

7.2.2 Temperature of calibration liquid ..................................................................................................................... 3

7.3 Cleanliness of surface ........................................................................................................................................................................ 4

7.4 Conditions of used volumetric instruments .................................................................................................................. 4

7.5 Delivery time and waiting time................................................................................................................................................. 4

8 Setting the meniscus ......................................................................................................................................................................................... 4

8.1 General ........................................................................................................................................................................................................... 4

8.2 Setting the meniscus .......................................................................................................................................................................... 5

8.2.1 Meniscus of transparent liquids ......................................................................................................................... 5

8.2.2 Meniscus of opaque liquids .................................................................................................................................... 6

9 Calibration procedure ..................................................................................................................................................................................... 6

9.1 General ........................................................................................................................................................................................................... 6

9.2 Test room ..................................................................................................................................................................................................... 7

9.3 Filling and delivery .............................................................................................................................................................................. 7

9.3.1 Volumetric flasks and measuring cylinders .................. ............................................................................ 7

9.3.2 Pipettes adjusted to deliver .................................................................................................................................... 7

9.3.3 Pipettes adjusted to contain .................. ................................................................................................................. 8

9.3.4 Burettes adjusted to deliver ................................................................................................................................... 8

9.4 Weighing ....................................................................................................................................................................................................... 8

9.5 Volume and uncertainty calculation ..................................................................................................................................... 9

10 Use ....................................................................................................................................................................................................................................10

10.1 General ........................................................................................................................................................................................................10

10.2 Volumetric flasks (see ISO 1042 or ISO 5215) ......... .................................................................................................10

10.3 Measuring cylinders (see ISO 4788 or 6706) ............................................................................................................11

10.4 Burettes (see ISO 385) ..................................................................................................................................................................11

10.5 Pipettes .......................................................................................................................................................................................................11

Annex A (informative) Cleaning of volumetric glassware ...........................................................................................................12

Annex B (informative) Cleaning of volumetric plasticware .......................................................................................................13

Annex C (normative) Calculation formulas and tables ...................................................................................................................14

Annex D (informative) Coefficient of cubical thermal expansion .......................................................................................18

Annex E (informative) Repeatability and uncertainty calculation .....................................................................................19

Bibliography .............................................................................................................................................................................................................................20

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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)
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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

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 48, Laboratory equipment, WG7-

Volumetric apparatus made of glass and plastic.

This third edition cancels and replaces the second edition (ISO 4787:2010), which has been technically

revised.
The main changes compared to the previous edition are as follows:
a) plastic ware was included;
b) new information on meniscus adjustment of convex meniscus;
c) improved figures for meniscus adjustment;
d) Table 1 was improved;
e) new Table 2 for minimum requirements for the measurement devices;
f) new test room ambient conditions;
g) new information regarding repeatability and uncertainty added in Annex E;
h) Formula (C.1) was changed to Formula (1).

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.
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oSIST prEN ISO 4787:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 4787:2021(E)
Laboratory glass and plastic ware — Volumetric
instruments — Methods for testing of capacity and for use
1 Scope

This International Standard provides methods for the testing, calibration and use of volumetric

instruments made from glass and plastic in order to obtain the best accuracy in use.

NOTE Testing is the process by which the conformity of the individual volumetric instrument with the

appropriate standard is determined, culminating in the determination of its error of measurement at one or

more points.

The International Standards for the individual volumetric instruments include clauses on the definition

of capacity; these clauses describe the method of manipulation in sufficient detail to define the capacity

without ambiguity. This International Standard contains supplementary information.

The procedures are applicable to volumetric instruments with nominal capacities in the range of 100 µl

to 10 000 ml. These include single-volume pipettes (see ISO 648), graduated measuring pipettes and

dilution pipettes (see ISO 835), burettes (see ISO 385), volumetric flasks (see ISO 1042), and graduated

measuring cylinders (see ISO 4788 and ISO 6706).

The procedures are not recommended for testing of volumetric instruments with capacities below

100 µl such as micro-glassware.

This International Standard does not deal specifically with pycnometers as specified in ISO 3507.

However, the procedures specified below for the determination of volume of glassware can, for the

most part, also be followed for the calibration of pycnometers.
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 385, Laboratory glassware — Burettes
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 835, Laboratory glassware — Graduated pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 1773, Laboratory glassware — Narrow-necked boiling flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 4788, Laboratory glassware — Graduated measuring cylinders

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and

associated terms (VIM)
ISO 6706, Plastics laboratory ware — Graduated measuring cylinders

ISO/IEC Guide 98:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)
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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC Guide 99 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Summary of method

The general procedure for testing of capacity and for use is based upon a determination of volume of

water, either contained in or delivered by the volumetric instrument. This volume of water is based

upon knowledge of its mass under consideration of buoyancy and its density (gravimetric method).

5 Volume and reference temperature
5.1 Unit of volume

The unit of volume shall be the millilitre (ml), which is equivalent to one cubic centimetre (cm ).

5.2 Reference temperature

The standard reference temperature, i.e. the temperature at which the volumetric instrument is

intended to contain or deliver its volume (capacity), shall be 20 °C.

When the volumetric instrument is required for use in a country which has adopted a standard

reference temperature of 27 °C (the alternative recommended in ISO 384 for tropical use), this figure

shall be substituted for 20 °C.
6 Apparatus and calibration liquid
6.1 Analytical balance or equivalent weighing device.

The balance used for testing shall be chosen according the specified minimum requirements of Table 1,

depending on the nominal volume of the volumetric instrument under test.
Table 1 — Minimum requirements for the balance
Expanded uncertainty in
Nominal capacity Readability Repeatability
use U (k = 2)
V mg mg mg
100 µl ≤ V ≤ 10 ml 0,1 0,2 0,4
10 ml < V ≤ 1 000 ml 1 2 4
V > 1 000 ml 10 10 40

Expanded uncertainty in use obtained according to EURAMET CG-18 [2] (which includes applicable definitions) at the

value of the nominal volume. If uncertainty in use is not available, then the uncertainty at calibration should be taken.

6.2 Measurement devices

The minimum requirements for each relevant measurement device are described in Table 2.

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oSIST prEN ISO 4787:2021
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Table 2 — Minimum requirements for the measurement devices
Expanded uncertainty of meas-
urement
Parameter Readability
(k = 2)
Thermometer for liquids 0,1 °C 0,2 °C
Thermometer for room air 0,1 °C 0,2 °C
Hygrometer 1 % rel. humidity 5 % rel. humidity
Barometer 0,1 kPa 1 kPa
Timing device 1 s Not applicable

6.3 Calibration liquid, distilled or deionized water complying with ISO 3696, Grade 3 should be used

for testing. The water temperature shall be within ±0,5 °C of ambient air temperature.

6.4 Receiving vessel, conical flask, if possible, with ground joint, manufactured from glass, e.g. in

accordance with ISO 1773, ISO 4797, or ISO 24450. The receiving vessel shall have a capacity adequate to

the amount of water delivered by the volumetric instrument.
7 Factors affecting the accuracy of volumetric instruments
7.1 General

The same sources of error are, naturally, inherent both in calibration and use. In the former, every

attempt is made to reduce these errors to a minimum; in the latter, the care needed is dependent

upon the degree of accuracy required. When the greatest possible accuracy is desired, the volumetric

instrument should be used as closely as possible to the way it has been calibrated.

7.2 Temperature
7.2.1 Temperature of the volumetric instrument

7.2.1.1 The capacity of the volumetric instruments varies with change of temperature. The particular

temperature at which a volumetric instrument is intended to contain or deliver its nominal capacity is

the “reference temperature” of the instrument (see 5.2).

7.2.1.2 A volumetric instrument which was calibrated at 20 °C, but used at a reference temperature of

27 °C, would show an extra error of only 0,007 % if it is made of borosilicate glass having a coefficient

−6 −1

of cubical thermal expansion of 9,9 × 10 °C and of 0,02 % if it is made of soda-lime glass having a

−6 −1.

coefficient of cubical thermal expansion of 27 × 10 °C , respectively. These errors are smaller than the

limits of error for most volumetric instruments. When performing calibrations, it is important to refer to

the reference temperature.
7.2.2 Temperature of calibration liquid

The temperature of the water used for the calibration shall be measured to ±0,1 °C, with a maximum

variation of ±1 °C during the test. Corrections for differences in temperature, prevailing during testing

or use, from the reference temperature shall be applied in accordance with Formula (1), 9.5 and

Annex C. The liquid temperature should be measured in the vessel where the instruments are filled

from or directly inside the instruments if technically possible.
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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)
7.3 Cleanliness of surface

The volume contained in, or delivered by, of a volumetric instrument depends on the cleanliness of the

internal surface. Lack of cleanliness of glass surface results in errors through a poorly shaped meniscus

involving two defects:

— incomplete wetting of the glass surface, i.e. the liquid surface meets the glass at an arbitrary angle

instead of forming a curve such that it meets the glass tangentially;

— a generally increased radius of curvature, due to contamination of the liquid surface reducing the

surface tension.

Volumetric instruments made of polyolefins, such as Polypropylene (PP) and Polymethylpentene (PMP),

or fluoroplastics, such as Perfluoroalkoxy-Copolymer (PFA), have water-repellent surfaces which

results in a poorly shaped convex or even flat meniscus (see 8.2 and 8.3).

The ascending or descending liquid meniscus shall not change shape (i.e. it shall not crinkle at its edges).

To ascertain whether a piece of apparatus is satisfactorily clean, it shall be observed during filling

and dispensing. Additionally, an experienced operator can recognize the shape of an uncontaminated

meniscus, in relation to its diameter.

Lack of cleanliness causes additional errors with volumetric instruments used for delivery due to

the film of liquid on the walls being irregularly distributed or incomplete, e.g. forming drops on the

glass surface. Furthermore, chemical residues can introduce an error in the analytical result by

contamination. Therefore, where volumetric instruments are fitted with ground stoppers, special

attention shall be paid to cleaning the ground zone.

NOTE Small residues of acid, for example, could impair the concentration of the alkaline solution with which

the volumetric instrument is filled.
Satisfactory methods of cleaning are described in Annex A and Annex B.
7.4 Conditions of used volumetric instruments

The surface shall be free from obvious damage, the graduations and inscriptions shall be clearly

readable and especially with instruments adjusted to deliver the jet shall be free from damage and

allow an unrestricted outflow of liquid.
7.5 Delivery time and waiting time

For volumetric instruments used for delivery of a liquid, the volume delivered is always less than the

volume contained, due to the film of liquid left on the inner walls of the volumetric instrument. The

volume of this film depends on the time taken to deliver the liquid, and the volume delivered decreases

with decreasing delivery time. For example, the delivered volume of a pipette or burette will decrease

if the jet is broken (shorter delivery time) or will increase if the jet is not clean and the outflow of liquid

is restricted.

In view of the above, delivery times and waiting times have been specified in the International Standards

on volumetric instruments; these times shall be observed.
8 Setting the meniscus
8.1 General

Most volumetric instruments employ the principle of setting or reading a meniscus (the interface

between air and the liquid) against a graduation line or ring mark. Wherever practicable, the meniscus

should descend to the position of setting.
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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)

The tubing of the volumetric instrument shall be in a vertical position. The eye of the operator shall be

in the same horizontal plane as the meniscus or the graduation line (graduation mark).

8.2 Setting the meniscus
8.2.1 Meniscus of transparent liquids

In case of a concave meniscus, the meniscus shall be set so that the plane of the upper edge of the

graduation line is horizontally tangential to the lowest point of the meniscus, the line of sight being in

the same plane (see Figure 1).
Key
1 Meniscus
2 Graduation line
3 dark coloured paper
Figure 1 — Setting of concave meniscus

In case of a convex or even flat meniscus, known for water-repellent, non-wetting surfaces of polyolefins,

such as PP and PMP, or fluoroplastics, such as PFA, the meniscus shall be set so that the plane of the

upper edge of the graduation line is horizontally tangential to the highest point of the meniscus, the line

of sight being in the same plane (see Figure 2).
Key
1 Meniscus
2 Graduation line
3 dark coloured paper
Figure 2 — Setting of convex meniscus (left) or even flat (right)

In case that an instrument showing a convex or even flat meniscus was calibrated according to the

procedure noted in the previous version of ISO 4787 (upper edge of the graduation line is horizontally

tangential to the lowest point of the meniscus) differences by setting meniscus with the procedure

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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)

mentioned above (upper edge of the graduation line is horizontally tangential to the highest point of the

meniscus) shall be corrected. These differences can lead to very significant values with respect to the

error limit.

On volumetric instruments fitted with a Schellbach ribbon, the meniscus shall be set using the

constriction produced by the interaction between the meniscus and the Schellbach ribbon. Setting is

done when the tip of the constriction points to the graduation line (see Figure 3).

Key
1 Meniscus
2 Graduation line
3 dark coloured paper
Figure 3 — Setting of meniscus with Schellbach ribbon

The lighting should be arranged so that the meniscus appears dark and distinct in outline. For this

purpose, it should be viewed against a white background and shaded from undesirable illumination.

This can be achieved, for example, by securing a strip of black or blue paper directly below the level of

the graduation line or ring mark or by using a short section of thick black rubber tubing cut open at one

side and of such size as to clasp the tube firmly. Parallax is avoided when the graduation lines are of

sufficient length to be seen at the front and back of the volumetric instrument simultaneously.

On volumetric instruments which have graduation lines on the front only, parallax can be made

negligible when making a setting on the top edge of the line by using the black shading strip, taking

care that the top edge of this is in a horizontal plane. In this case, the eye shall be placed so that the

front and back portions of the top edge appear to be coincident.
8.2.2 Meniscus of opaque liquids

When the volumetric instrument is used with opaque wetting liquids forming a concave meniscus, the

horizontal line of sight shall be taken through the upper edge of the meniscus, and, where necessary, an

appropriate correction shall be applied.

In case of a convex or even flat meniscus, the meniscus shall be set so that the plane of the upper edge of

the graduation line is horizontally tangential to the highest point of the meniscus, the line of sight being

in the same plane, and, where necessary, an appropriate correction shall be applied.

9 Calibration procedure
9.1 General

Volumetric instruments other than disposable pipettes shall be thoroughly cleaned shortly before

calibration (see 7.3). Volumetric instruments adjusted to contain shall be dried after cleaning.

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oSIST prEN ISO 4787:2021
ISO/DIS 4787:2021(E)

For volumetric instruments adjusted to deliver, it is important that receiving vessels manufactured

from glass are used. Capillary effects influencing the delivery time and the delivered volume depend

considerably on the material on which the liquid runs down
...