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IS0
I N T E RN AT I O N A L ORGAN I2 AT 1 ON FOR STAND AR D IZATlO N
I SO R ECO M M EN DATI O N
R 684
ANALYSIS OF SOAPS
DETERMINATION OF TOTAL FREE ALKALI
1 st EDITION
March 1968
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belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 684, Analysis of soaps - Determination of total fiee alkali, was
drawn up by Technical Committee ISO/TC 91, Surface active agents, the Secretariat of which is held
by the Association Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1963 and led, in 1964, to the
adoption of a Draft IS0 Recommendation.
L.
In December 1965, this Draft IS0 Recommendation (No. 934) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
:
by the following Member Bodies
Argentina Hungary South Africa,
Australia Ireland Rep. of
Austria Israel Spain
Belgium Japan Switzerland
Brazil Netherlands Tutkey
U.A.R.
Canada New Zealand
United Kingdom
Chile Poland
France Portugal Yugoslavia
Germany Romania
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council
which decided, in March 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 684-1968 (E
IS0 Recommendation R 684 March 1968
ANALYSIS OF SOAPS
DETERMINATION OF TOTAL FREE ALKALI
1. SCOPE
This IS0 Recommendation describes the method for the determination of total free alkali in soaps,
excluding compounded products. *
1.1 Field of application
The method is not applicable when the soap contains additives which can be decomposed by
fatty acids under the operating conditions described (alkali silicates, etc.).
The method is not applicable to coloured soaps, if the colour interferes with the phenolphthalein
end point.
2. DEFINITION
By total free aZkuZi is understood the sum of the free caustic alkali and the free alkali as carbonate,
expressed conventionally as sodium hydroxide (NaOH) for sodium soaps and as potassium hydroxide
(KOH) for potassium soaps.
3. PRINCIPLE
Dissolution of the soap in an ethanolic solution of fatty acids, the excess of which is titrated with an
ethanolic solution of potassium hydroxide.
4. REAGENTS
4.1 Ethanol, 80 'A (v/v) solution freed from carbon dioxide by boiling for 5 minutes under a reflux
condenser.
Cool to ambient temperature and neutralize by means of the ethanolic potassium hydroxide
solution (4.2) in the presence of phenolphthalein (4.4) (four drops per 200 mi).
4.2 Potassium hydroxid
...