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Ref. No. : ISO/R 673-1968 (E)
IS0
I NTERN AT ION A L O RG A N IZATl O N FOR STAND ARDlZ ATiON
IS0 RECOMMENDATION
R 673
ANALYSIS OF SOAPS
DETERMINATION OF FOREIGN MATTER
OF LOW SOLUBILITY IN ETHANOL
1 st EDITION
February 1968
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The copyright of IS0 Recommendations and IS0 Standards
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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 673, Analysis of soaps - Determination of foreign matter of low
solubility in ethanol, 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 adoption
of a Draft IS0 Recommendation.
In October 1965, ths Draft IS0 Recommendation (No. 834) 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 :
South Africa,
Argentina Hungary
Rep. of
Austria Ireland
Spain
Belgium Israel
Sweden
Brazil Japan
Canada Netherlands Switzerland
Chile New Zealand U.A.R.
Colombia Poland United Kingdom
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 February 1968 to accept it as an IS0 RECOMMENDATION.
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ISO/R 673-1968 (E
IS0 Recommendation R673 February 1968
ANALYSIS OF SOAPS
DETERMINATION OF FOREIGN MATTER
OF LOW SOLUBILITY IN ETHANOL
1. SCOPE
The purpose of this IS0 Recommendation is to provide a method of qualitative examination for
foreign matter contained in commercial soaps, excluding compounded products, and of low solubility
in ethanol, and to specify the method of determining them quantitatively. This foreign matter may be
inorganic (carbonates, borates, perborates, chlorides, sulphates, silicates, phosphates, iron oxide, etc.)
or organic (starches, dextrines, caseins, sugars, cellulose derivatives, alginates, etc.).
2. PRINCiPLE
(applicable to both qualitative examination and quantitative determination)
Dissolution of the soap in ethanol. The undissolved residue represents the “foreign matter of low
solubility in ethanol”.
3. QUALITATIVE EXAMINATION
3.1 Reagent
Ethanol, 95 ‘Io (v/v).
3.2 Apparatus
3.2.1 Conical flask, 400 to 500 ml, preferably with a ground-glass neck, which can be fitted to a
reflux condenser.
3.2.2 Reflux condenser, preferably with a ground-glass neck.
3.2.3 Measuring cylinder, 1 O0 ml.
3.2.4 Anab tical balance.
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ISO/R 673-1968 (E)
I
3.3 Procedure
3.3.1 Test portion. Weigh about 5 g of the previously dried sample into the conical flask.
NOTE. - In the case of soaps in which the water content is high (liquid soaps, soft soaps) weigh a larger
quantity of the sample. sufficient to yield about 5 g of dry residue, and evaporate to dryness.
3.3.2 Examination., Add to the test portion about 100 ml of the ethanol (3.1). Connect to the
reflux condenser. Bring to a gentle boil and keep at the boil until the soap has completely
dissolved. The undissolved portion is due to the presence of foreign matter in the soap.
Actually, under the conditions of the experiment, small amounts of substances accompany-
ing all soaps (alkali carbonate and chloride) pass into solution.
4. QUANTITATIVE DETERMINATION
4.1 Reagent
Ethanol, absolute.
4.2 Apparatus
Usual laboratory apparatus not otherwise specified and the following items :
4.2.1 Evaporating dish.
4.2.2 Stirring rod.
4.2.3 Conical flasks, 400 to 500 ml, preferably with ground-glass neck, which can be fitted to a
reflux condenser.
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4.2.4 Reflux condenser, preferably with ground-glass neck.
4.2.5 Water-bath.
4.2.6 Filter paper. *
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