ISO 3682:1976

INTERNATIONAL STANDARD 3682
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INTERNATIONAL ORGANIZATION FOR STANDARDIZATION *MEXAYHAPOAHAR OPrAHH3AUCIR IT0 CTAHLIAPTHJAUACI .ORGANISATION INTERNATIONALE DE NORMALISATION
* Paint media - Determination of acid value - Titrimetric
method
Liants pour peintures - Détermination de l'indice d'acide - Méthode titrimétrique
First edition - 1976-09-01
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UDC 667.6 : 543.852.1 Ref. No. IS0 3682-1976 (E)
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Descriptors : paints, binders (materials), chemical tests, determination, acid number, volumetric analysis.
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Price based on 2 pages

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FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 Member Bodies). The work of developing
International Standards is carried out through IS0 Technical Committees. Every
Member Body interested in a subject for which a Technical Committee has been set
up 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.
Draft International Standards adopted by the Technical Committees are circulated
I to the Member Bodies for approval before their acceptance as International
Standards by the IS0 Council.
International Standard IS0 3682 was drawn up by Technical Committee
iSO/TC 35, Paints and varnishes, and was circulated to the Member Bodies in
January 1975.
It has been approved by the Member Bodies of the following countries :
Austria I ran Romania
South Africa, Rep. of
Brazil Ireland
Bulgaria Israel Spain
Mexico Sweden
Canada
Chile Netherlands Switzerland
France New Zealand Turkey
United Kingdom
Germany Poland
India Portugal Yugoslavia
The Member Body of the following country expressed disapproval of the document
on technical grounds :
Italy
O International Organization for Standardization, 1976
Printed in Switzerland

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INTERNATIONAL STANDARD IS0 3682-1976 (E)
Paint media - Determination of acid value - Titrimetric
method
5.3 Phenolphthalein, indicator solution, 1 O g/I in ethanol
1 SCOPE AND FIELD OF APPLICATION
95 % (V/V), or other suitable indicator, for example
This International Standard specifies a titrirn tric rn thod
bromothymol blue, 1 O g/I in ethanol 95 % (V/V).
for the determination of the acid value of paint media. It is
not applicable to phenolic resins.
6 APPARATUS
Ordinary laboratory apparatus and
2 REFERENCE
6.1 Conical flask, capacity 250 ml.
IS0 842, Raw materials for paints and varnishes -
Sampling.
6.2 Burette, capacity 50 ml.
3 DEFINITION
If required :
acid value : The number of milligrams of potassium 6.3 Device for potentiometric titration, with glass
hydroxide (KOH) required to neutralize the free acids
electrode and reference electrode.
contained in 1 g of the product.
6.4 Magnetic stirrer.
NOTE - If free acid anhydrides are present in the paint medium,
as in the case of certain polyester resins, the alcoholic potassium
hydroxide solution reacts only partially with the anhydrides; this,
7 PROCEDURE
however, is generally of little importance with most paint media
because of the small amount of free anhydrides present.
7.1 Test portion
The mass of the test portion depends on the acid value to
be expected (approximate values are given in the table).
e 4 SAMPLING
This mass shall be chosen so that the volume of the
A representative sample of the product to be tested shall be
potassium hydroxide solution (5.2) is in the range 10 to
taken as descibed in IS0 842.
30 ml.
Weigh, to the nearest 0,001 g, the test portion into the
5 REAGENTS
conical flask (6.1).
During the analysis, use only reagents of recognized
analytical reagent grade.
Masof test
Expected
5.1 Solvent mixture, consisting of 2 parts by volume of
toluene and 1 part by volume of ethanol, at least
mg KOH/g
9
95 % (V/V),l) if not otherwise agreed or specified.
Neutralize the solvent mixture with the 0,l N potassi
...