Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric titration

Describes the procedure for the determination of the acidity of unused and used electrical mineral insulating oils. The method may be used to indicate relative changes that occur in a mineral insulating oil during use under oxidizing conditions regardless of the colour or other properties of the resulting mineral oil. The acidity can be used in the quality control of unused mineral oil. As a variety of oxidation products present in used mineral oil contribute to acidity and these products vary widely in their corrosion properties, the test cannot be used to predict corrosiveness of a mineral oil under service conditions. The acidity results obtained by this test method may or may not be numerically the same as those obtained by colorimetric methods, but they are generally of the same magnitude.

Isolierflüssigkeiten - Bestimmung des Säuregehaltes - Teil 1: Automatische potentiometrische Titration

Liquides isolants - Détermination de l'acidité - Partie 1: Titrage potentiométrique automatique

Décrit la procédure pour la détermination de l'acidité des huiles isolantes minérales électriques neuves et usagées. La méthode peut être utilisée pour indiquer des modifications relatives qui se produisent dans une huile minérale isolante pendant son utilisation par oxydation, indépendamment de la couleur ou d'autres propriétés de l'huile. L'acidité peut être utilisée dans le contrôle de la qualité des huiles minérales neuves. Comme divers produits d'oxydation présents dans l'huile minérale usagée contribuent à l'acidité et comme ces produits varient largement du point de vue de leurs propriétés de corrosion, l'essai ne peut pas être utilisé pour prévoir la corrosivité d'une huile minérale dans des conditions de service. Les résultats d'acidité obtenus par cette méthode d'essai peuvent ou peuvent ne pas être numérique-ment les mêmes que ceux obtenus par des méthodes colorimétriques, mais ils sont généralement du même ordre de grandeur.

Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric titration (IEC 62021- 1:2003)

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SLOVENSKI SIST EN 62021-1:2004

april 2004
Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric
titration (IEC 62021- 1:2003)
ICS 29.040.10 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno


ICS 29.040.10; 29.180
English version
Insulating liquids -
Determination of acidity
Part 1: Automatic potentiometric titration
(IEC 62021-1:2003)
Liquides isolants -  Isolierflüssigkeiten -
Détermination de l'acidité Bestimmung des Säuregehaltes
Partie 1: Titrage potentiométrique Teil 1: Automatische potentiometrische
automatique Titration
(CEI 62021-1:2003) (IEC 62021-1:2003)

This European Standard was approved by CENELEC on 2003-09-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62021-1:2003 E
The text of document 10/559/FDIS, future edition 1 of IEC 62021-1, prepared by IEC TC 10, Fluids for
electrotechnical applications, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 62021-1 on 2003-09-01.

The following dates were fixed:

– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2004-06-01

– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2006-09-01

Annexes designated "normative" are part of the body of the standard.
In this standard, annex ZA is normative.
Annex ZA has been added by CENELEC.
Endorsement notice
The text of the International Standard IEC 62021-1:2003 was approved by CENELEC as a European
Standard without any modification.
- 3 - EN 62021-1:2003
Annex ZA
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60475 - Method of sampling liquid dielectrics - -

Undated reference.
Première édition
First edition
Liquides isolants –
Détermination de l'acidité –
Partie 1:
Titrage potentiométrique automatique
Insulating liquids –
Determination of acidity –
Part 1:
Automatic potentiometric titration
© IEC 2003 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail:  Web:
Commission Electrotechnique Internationale PRICE CODE
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

62021-1 © IEC:2003 – 3 –
1 Scope . 9
2 Normative references. 9
3 Terms and definitions . 9
4 Principle .11
5 Reagents and auxiliary products .11
5.1 Reagents .11
5.2 Titration reagent .11
5.3 Titration solvent.11
5.4 Potassium hydrogen phthalate, primary standard.11
5.5 Potassium chloride reference electrolyte.13
5.6 Aqueous buffer solutions .13
5.7 Cleaning solution.13
6 Apparatus .13
6.1 Potentiometric titration apparatus .13
6.2 Glass indicating electrode.13
6.3 Reference electrode .13
6.4 Stirrer .15
6.5 Titration vessel .15
6.6 Titration stand .15
7 Sampling .15
8 Preparation and maintenance of electrode system .15
9 Calibration of apparatus.17
10 Procedure.17
10.1 Standardization of alcoholic potassium hydroxide solution .17
10.2 Blank titration .19
10.3 Sample titration .19
11 Calculation.21
12 Precision .21
12.1 Repeatability.21
12.2 Reproducibility.21
13 Report .23

62021-1 © IEC:2003 – 5 –
Part 1: Automatic potentiometric titration
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62021-1 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
The text of this standard is based on the following documents:
FDIS Report on voting
10/559/FDIS 10/564/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until 2012.
At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
62021-1 © IEC:2003 – 7 –
General caution
This International Standard does not purport to address all the safety problems associated
with its use. It is the responsibility of the user of the standard to establish appropriate health
and safety practices and determine the applicability of regulatory limitations prior to use.
The insulating liquids which are the subject of this standard should be handled with due
regard to personal hygiene. Direct contact with the eyes may cause slight irritation. In the
case of eye contact, irrigation with copious quantities of clean running water should be carried
out and medical advice sought.
Some of the procedures referenced in this standard involve the use of processes that could
lead to a hazardous situation. Attention is drawn to the relevant standard for guidance.
This standard gives rise to mineral insulating oils, chemicals, used sample containers and
fluid-contaminated solids. The disposal of these items should be carried out according to local
regulations with regard to their impact on the environment. Every precaution should be taken
to prevent the release into the environment of these oils.

62021-1 © IEC:2003 – 9 –
Part 1: Automatic potentiometric titration
1 Scope
This part of IEC 62021 describes the procedure for the determination of the acidity of unused
and used electrical mineral insulating oils.
NOTE 1 In unused and used mineral insulating oils, the constituents that may be considered to have acidic
characteristics include organic acids, phenolic compounds, some oxidation products, resins, organometallic salts
and additives.
The method may be used to indicate relative changes that occur in a mineral insulating oil
during use under oxidizing conditions regardless of the colour or other properties

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