Insulating liquids - Determination of acidity - Part 2: Colourimetric titration

Describes a procedure for 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 that may or may not be shown by 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.

Liquides isolants - Détermination de l'acidité - Partie 2: Titrage colorimétrique

Décrit une 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 l'utilisation dans des conditions d'oxydation qui peuvent être ou peuvent ne pas être révélées par d'autres propriétés de l'huile minérale résultante. 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.

General Information

Status
Published
Publication Date
14-May-2007
Current Stage
PPUB - Publication issued
Start Date
15-May-2007
Completion Date
15-May-2007
Ref Project

Buy Standard

Standard
IEC 62021-2:2007 - Insulating liquids - Determination of acidity - Part 2: Colourimetric titration
English and French language
32 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

INTERNATIONAL IEC
STANDARD
CEI
62021-2
NORME
First edition
INTERNATIONALE
Première édition
2007-05
Insulating liquids –
Determination of acidity
Part 2:
Colourimetric titration
Liquides isolants –
Détermination de l’acidité
Partie 2:
Titrage colorimétrique
Reference number
Numéro de référence
IEC/CEI 62021-2:2007
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2007 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester.

If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,

please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite

ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie

et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.

Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette

publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub

The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).

It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub

Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available

on-line and also by email.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv

If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service

Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
A propos de la CEI

La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des

normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI

Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez

l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
ƒ Catalogue des publications de la CEI: www.iec.ch/searchpub/cur_fut-f.htm

Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de

référence, texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou

remplacées.
ƒ Just Published CEI: www.iec.ch/online_news/justpub

Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles

publications parues. Disponible en-ligne et aussi par email.
ƒ Service Clients: www.iec.ch/webstore/custserv/custserv_entry-f.htm

Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du

Service clients ou contactez-nous:
Email: csc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
---------------------- Page: 2 ----------------------
INTERNATIONAL IEC
STANDARD
CEI
62021-2
NORME
First edition
INTERNATIONALE
Première édition
2007-05
Insulating liquids –
Determination of acidity
Part 2:
Colourimetric titration
Liquides isolants –
Détermination de l’acidité
Partie 2:
Titrage colorimétrique
PRICE CODE
CODE PRIX
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur
---------------------- Page: 3 ----------------------
– 2 – 62021-2 © IEC:2007
CONTENTS

FOREWORD...........................................................................................................................3

INTRODUCTION.....................................................................................................................5

1 Scope...............................................................................................................................6

2 Normative references .......................................................................................................6

3 Terms and definitions .......................................................................................................7

4 Principle ...........................................................................................................................7

5 Reagents..........................................................................................................................7

5.1 Titration reagent......................................................................................................7

5.2 Titration solvent.......................................................................................................8

5.3 Potassium hydrogen phthalate, primary standard ....................................................8

5.4 Standard hydrochloric acid solution .........................................................................8

5.5 Alkali Blue 6B indicator solution ..............................................................................8

5.6 Cobalt nitrate solution .............................................................................................8

6 Apparatus.........................................................................................................................8

6.1 Titration vessel........................................................................................................8

6.2 Stirrer......................................................................................................................8

6.3 Burette ....................................................................................................................8

7 Sampling ..........................................................................................................................8

8 Procedure ........................................................................................................................9

8.1 Standardization of alcoholic potassium hydroxide solution.......................................9

8.2 Blank titration ..........................................................................................................9

8.3 Sample titration .....................................................................................................10

9 Calculation of results ......................................................................................................10

10 Precision ........................................................................................................................10

10.1 Repeatability .........................................................................................................10

10.2 Reproducibility ......................................................................................................11

11 Report ............................................................................................................................11

Annex A (informative) Determination of acidity in electrical insulating oils by

photometric titration ..............................................................................................................12

Figure A.1 – Molecular structure of para-naphtolbenzein indicator in (I) acidic media

and (II) basic media ..............................................................................................................15

Figure A.2 – UV spectra of para-naphthol-benzein indicator in toluene/2-

propanol/water solution in (a) acidic media, (b) basic media .................................................16

---------------------- Page: 4 ----------------------
62021-2 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
INSULATING LIQUIDS –
DETERMINATION OF ACIDITY –
Part 2: Colourimetric titration
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). 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. 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 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 IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62021-2 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
10/692/FDIS 10/696/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.

---------------------- Page: 5 ----------------------
– 4 – 62021-2 © IEC:2007

A list of all parts of IEC 62021 series, under the general title Insulating liquids – Determination

of acidity can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
62021-2 © IEC:2007 – 5 –
INTRODUCTION

The standardized method given in IEC 62021-1 is a method for measurement of acidity in

used and unused mineral oil and is a potentiometric titration requiring special instrumentation

for measurement of acidity. Historically, acidity of insulating oil was measured by

colourimetric titration as described in IEC 60296, 1982 edition. With the revision of IEC 60296,

the colourimetric titration was deleted as that method used high volumes of sample and

solvent, generating undesirable volumes of waste.

However, there is still a market requirement for having colourimetric titration as many labs

use this method.
Health and safety

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 mineral oils which are the subject of this standard should be handled with due regard to

personal hygiene. Direct contact with 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 tests specified 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 involves mineral oils, chemicals and used sample containers. The disposal of

these items should be carried out in accordance with current national legislation with regard

to the impact on the environment. Every precaution should be taken to prevent the release

into the environment of mineral oil.
---------------------- Page: 7 ----------------------
– 6 – 62021-2 © IEC:2007
INSULATING LIQUIDS –
DETERMINATION OF ACIDITY –
Part 2: Colourimetric titration
1 Scope

This part of IEC 62021 describes a procedure for 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 that may or may not be shown by 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.

NOTE 2 The acidity results obtained by this test method may or may not be numerically the same as those

obtained by potentiometric methods, but they are generally of the same magnitude. The potentiometric method

uses an endpoint at pH 11,3 to ensure titration of all species, whereas the colourimetric methods uses an indicator

changing colour at approximately pH 9,5. This may lead to slightly higher results for oils with acidities above

0,3 mg KOH/g oil when using the potentiometric method.
2 Normative references

The following referenced documents are indispensable for the application 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.
IEC 60475: Method of sampling liquid dielectrics

IEC 60567: Oil-filled electrical equipment – Sampling of gases and of oil for analysis of free

and dissolved gases – Guidance
ISO 5725: Accuracy (trueness and precision) of measurement methods and results

ISO 6619: Petroleum products and lubricants – Neutralization number – Potentiometric

titration method
---------------------- Page: 8 ----------------------
62021-2 © IEC:2007 – 7 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acidity

quantity of base, expressed in milligrams of potassium hydroxide per gram of sample,

required to titrate colourimetrically a test portion in a specified solvent to the neutralization

point of Alkali Blue 6B
3.2
unused oil

mineral insulating oil that has not been used in, or been in contact with electrical equipment

4 Principle

The test portion is dissolved in a specified solvent and titrated colourimetrically with alcoholic

potassium hydroxide to a specified colour using Alkali Blue 6B indicator.
5 Reagents

Only reagents of recognized analytical grade and de-ionized water or water of equivalent

purity shall be used.
5.1 Titration reagent
Standard alcoholic solution 0,05 mol/l potassium hydroxide.

Add 3,0 g of potassium hydroxide to 1 000 ml ± 10 ml of 2-propanol. Boil gently for 10 min to

effect solution. Cool and stopper the flask.

Allow the solution to stand in the dark for 2 days and then filter the supernatant liquid through

a 5 μm membrane filter. Store in a suitable amber glass bottle.

The concentration of this solution is approximately 0,05 mol/l and shall be standardized as

described in 8.1. For periodic tests on equipment in service, faster titration may be achieved

by the use of 0,1 mol/l potassium hydroxide by agreement between the laboratory and the

equipment owner, although this may result in poorer precision and detection limit.

Commercial alcoholic potassium hydroxide solution may be used, if necessary diluting to

0,05 mol/l with 2-propanol. This shall be standardized as described in 8.1.

Store and use in such a manner that the solution is protected from atmospheric carbon

dioxide and in such a way that it does not come into contact with cork, rubber or saponifiable

stopcock grease. The solution may be protected by inert gas or by means of a guard tube

containing soda-lime absorbent.
---------------------- Page: 9 ----------------------
– 8 – 62021-2 © IEC:2007
5.2 Titration solvent
2-propanol (isopropanol; IPA), pure.
5.3 Potassium hydrogen phthalate, primary standard
This should be dried before use for 2 h at 105 °C.
5.4 Standard hydrochloric acid solution

A 0,1 mol/l solution of hydrochloric acid in de-ionized water, prepared as in ISO 6619, may be

used. Other acids may be used, provided they are certified against a primary standard.

5.5 Alkali blue 6B indicator solution

Dissolve 2 g ± 0.1 g of alkali blue 6B in 100 ml of 2-propanol or azeotropic ethanol containing

1 ml of the hydrochloric acid solution. After 24 h, carry out a titration to check whether the

indicator has been sufficiently sensitized. The indicator is satisfactory if the colour changes

distinctly from blue to red comparable to that of a 10 % solution of cobalt nitrate. If

sensitization is insufficient, repeat the addition of the hydrochloric acid solution and check

again after 24 h. Continue until sensitization is satisfactory. Filter and store in a brown bottle

in the dark.

Commercial alkali blue 6B solution may be used as an alternative if the concentration is within

the range 0,05 % to 5 %. If the concentration is not 2 %, the amount added to the solvent in

8.2 and 8.3 should be adjusted to maintain the same ultimate concentration.
5.6 Cobalt nitrate solution
Co(NO ) .6H O solution, 10 % in water.
3 2 2
6 Apparatus
6.1 Titration vessel

This should be as small as possible, sufficient to contain the solvent, sample and stirrer and

be inert to the reagents. Glass conical vessels are preferred.
6.2 Stirrer

Stirring may be manual by swirling the solution on the titration vessel, or mechanically using a

variable speed stirrer fitted with a propeller, paddle or magnetic bar of chemically inert

surface material.
6.3 Burette
A burette or syringe capable of adding aliquots of 0,001 ml shall be used.
7 Sampling

Samples shall be taken following the procedure given in IEC 60475 and/or IEC 60567.

Ensure that the test portion is representative by thoroughly mixing, as any sediment present

may be acidic or have adsorbed acidic material from the liquid phase.
---------------------- Page: 10 ----------------------
62021-2 © IEC:2007 – 9 –
8 Procedure

Rinse and fill the burette with 0,05 mol/l alcoholic potassium hydroxide solution (5.1).

Standardize the alcoholic potassium hydroxide solution at least every two weeks against

potassium hydrogen phthalate (5.3) or certified standard 0,1 mol/l acid.

Carry out a blank titration on the solvent (5.2) each day and after changing to a fresh batch of

solvent.
8.1 Standardization of alcoholic potassium hydroxide solution

Standardize the alcoholic potassium hydroxide solution, using a suitable indicator, against

0,1 g to 0,16 g of potassium hydrogen phthalate, weighed to an accuracy of 0,000 2 g and

dissolved in approximately 100 ml of carbon dioxide free water.
Alternatively the standardization can be performed by potentiometric titration.
Calculate the molarity M to the nearest 0,000 5 using Equation (1):
1 000 × m × p
Molarity = (1)
204,23 ×V
where
m is the mass of potassium hydrogen phthalate, in grams;
p is the percent purity of the potassium hydrogen phthalate;
V is the volume of potassium hydroxide solution, in millilitres.

Alternatively, certified standard 0,1 mol/l acid may be used to standardize the alcoholic

potassium hydroxide solution.
Calculate the molarity M to the nearest 0,000 5 using Equation (2):
V × M
1 A
Molarity = (2)
where

V is the volume of 0,1 mol/l standard acid used to titrate the solution, in millilitres;

M is the molarity of the standard hydrochloric acid;
V is the volume of potassium hydroxide solution, in millilitres.
8.2 Blank titration

Perform a blank titration at a temperature not above 25 °C on 10 ml ± 0,1 ml aliquots of the

solvent containing 0,5 % of alkali blue 6B indicator solution (5.5) using the standardized

alcoholic potassium hydroxide solution. The endpoint shall be as soon as a colour change

from blue to a red colour comparable to that of the cobalt nitrate solution (5.6) is obtained and

persists for at least 15 s.

Carry out triplicate titrations and calculate the mean result, in millilitres to the nearest

0,001 ml, as the blank value V .
---------------------- Page: 11 ----------------------
– 10 – 62021-2 © IEC:2007
Protect the solvent from atmospheric carbon dioxide and use within 8 h.
8.3 Sample titration

Weigh 5 g of sample to the nearest 0,01 g into the titration vessel. Add 10 ml ± 0,1 ml of the

solvent solution containing 0,5 % of alkali blue 6B indicator solution (5.5). Swirl to dissolve

the oil and immediately titrate at a temperature not above 25 °C with the standardized

potassium hydroxide solution. A typical end point is as described in 8.2. However, since the

colour change may vary for different oils, pre-titration may be necessary to establish this. In

such cases, the endpoint shall be reached as soon as a stable colour change, which persists

for at least 15 s, is obtained.

NOTE Before titrating, the colour may vary from blue to green and at the endpoint from red to light orange to dark

yellow-brown, depending on the original colour of the oil.

Carry out determinations for each oil sample and note the result, in millilitres, to the nearest

0,001 ml, as the titration value V .
9 Calculation of results

Calculate, for each determination, the acidity to the nearest 0,005, expressed as mg KOH/g of

oil, using Equation (3):
()V −V × M × 56,1
1 0
Acidity = (3)
where

V is the volume of alcoholic KOH solution used to titrate the test sample, in millilitres;

V is the mean volume of alcoholic KOH solution used for the blank titration, in millilitres;

M is the molarity of alcoholic KOH solution;
m is the mass of the test portion used, in grams.
10 Precision

The repeatability and reproducibility limits were established in accordance with ISO 5725.

10.1 Repeatability

The difference between successive test results obtained by the same operator with the same

apparatus under constant operating conditions on identical test material would, in the long run,

in the normal and correct operation of the test method, exceed the values shown below only in

one case in 20:
− unused oils –15 %;
− used oils –10 %.

NOTE The repeatability values for unused oils only apply where the result is significantly above the quantification

limit, which has been established as 0,01 mg KOH/g oil.
---------------------- Page: 12 ----------------------
62021-2 © IEC:2007 – 11 –
10.2 Reproducibility

The difference between two single and independent results obtained by different operators

working in different laboratories on identical test material would, in the long run, in the normal

and correct operation of the test method, exceed the values shown below only in one case

in 20:
− unused oils – 35 %;
− used oils – 20 %.

NOTE The reproducibility values for unused oils only apply where the result is significantly above the

quantification limit, which has been established as 0,01 mg KOH/g oil.
11 Report
The test report shall contain at least the following information.
– The type and identification of the product tested.
– A reference to this International Standard.

– The result of the test (see Clause 9) expressed to the nearest 0,01 mg KOH/g of oil.

– Any deviation, by agreement or otherwise, from the procedure specified.
– The date of the test.
---------------------- Page: 13 ----------------------
– 12 – 62021-2 © IEC:2007
Annex A
(informative)
Determination of acidity in electrical insulating oils
by photometric titration
A.1 Principle

A sample of new or used oil is dissolved in a mixture of toluene and 2-propanol containing a

small amount of water. The solution is titrated at ambient temperature with alcoholic

potassium hydroxide. The neutralization of acid components in oil is detected by the colour

change of the added para-naphtolbenzein indicator, using a photometric sensor at 660 nm.

A.2 Reagents and solvents
– Para-naphtolbenzein indicator (1 % in alcoholic solution)
– Potassium hydroxide solution in 2-propanol (1 mol/l)
– Potassium hydrogen phthalate
– 2-Propanol, anhydrous, HPLC grade
– Toluene, HPLC grade
– Demineralized water, conductivity < 0,1 μS/cm
– Methanol, HPLC grade
– CO absorbing agent, 8-20 mesh
– Water absorbing agent, 10-20 mesh

NOTE It is recommended to filter all solvents, solutions and oil samples prior to use.

A.2.1 Preparation of titration solutions and solvents
A.2.1.1 Potassium hydroxide alcoholic solution (0,05 mol/l)

Introduce 50 ml of the potassium hydroxide solution in 2-propanol (1 mol/l) into a volumetric

vessel of 1 l. Make up to 1,0 l with 2-propanol.
A.2.1.2 Potassium hydrogen phthalate solution (0,05 mol/l)

Crush 10 g of potassium hydrogen phthalate in a mortar and dry at 120 °C for 1 h, then cool in

a desiccator containing a water-absorbing agent. Weigh about 5 g of dried potassium

hydrogen phthalate precisely in a scoop and introduce it in a volumetric vessel of 500 ml.

Wash the scoop several times with small amounts of water into the volumetric vessel. Make

up to 500,0 ml with demineralised water.
Calculate the molarity to the nearest 0,000 5 using following Equation (A.1):
Molarity (M KPH) = (A.1)
204,23 × 0,5
where m is the mass of potassium hydrogen phthalate, in gram.
---------------------- Page: 14 ----------------------
62021-2 © IEC:2007 – 13 –
A.2.1.3 Titration solvent

The composition of the titration solvent in % volume/volume is: 50 % toluene, 49,5 %

2-propanol, 0,5 % demineralized water. 500 μl of para-naphtolbenzein indicator solution is

added per 100 ml of titration solvent.
A.3 Apparatus
A.3.1 Volumetric titrator

The apparatus shall be equipped with an automatic burette of 5 ml capacity with a dispensing

accuracy of ±0,01ml. A guard tube containing the water and carbon dioxide absorbing agents

is necessary for the reservoir for the alcoholic potassium hydroxide solution.
A.3.2 Titration vessel
The titration vessel shall have a 100 ml capacity and be inert to the reagents.

NOTE The vessel volume should be such that the photometer probe is covered by liquid during the titration.

A.3.3 Titration stand

A suitable stand shall be provided to support the titration vessel, stirrer, automatic burette and

photometric sensor.
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.