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Kef. No. : ISO/R 741-1968 (E)
IS0
I N T ERN AT I ON A L ORGANIZATION FOR STAND A RD IZ AT10 N
IS0 RECOMMENDATION
R 741
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF SODIUM HYDROGEN CARBONATE
VOLUMETRIC METHOD
1st EDITION
May 1968
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The copyright of IS0 Recommendations and IS0 Standards
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 74 1, Sodium carbonate for industrial use - Determination of
sodium hydrogen carbonate - Volumetric method, was drawn up by Technical Committee
Chemism, the Secretariat of which is held by the Ente Nazionale Italian0 di Unificazione
ISO/TC 47,
(UNI).
Work on this question by the Technical Committee began in 1951 and led, in 1956, to the
adoption of a Draft IS0 Recommendation.
IS0 Recommendation (No. 1007) was circulated to all the IS0
In June 1966, this Draft
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by
the following Member Bodies :
Italy Switzerland
Argentina
Japan Turkey
Austria
Belgium Korea, Rep. of U.A.R.
Brazil Netherlands United Kingdom
Chile New Zealand U.S.S.R.
Poland Yugoslavia
Czechoslovakia
France Portugal
Germany Romania
Hungary South Africa,
Rep. of
India
Spain
Israel
One Member Body opposed the approval of the Draft :
U.S.A.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in May 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 741-1968 (E)
IS0 Recommendation R 741 May 1968
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF SODIUM HYDROGEN CARBONATE
VOLUMETRIC METHOD
1. SCOPE
This IS0 Recommendation describes a volumetric method for the determination of the sodium hydro-
gen carbonate content in sodium carbonate for industrial use.
2. PRINCIPLE
Conversion of the sodium hydrogen carbonate contained in the test portion into sodium carbonate by
addition of a known excess of sodium hydroxide.
Precipitation of ail the carbonate by means of barium chloride.
Determination of the excess of sodium hydroxide by means of a standard volumetric solution of
hydrochloric acid using phenolphthalein as indicator. The amount of sodium hydroxide used corres-
ponds to the sodium hydrogen carbonate contained in the test portion.
3. REAGENTS
Distilled water or water of equivalent purity free from carbon dioxide at room temperature should be
used in the test.
Eliminate any carbon dioxide present, either by boiling the water for 10 minutes and then cooling in
the absence of atmospheric carbon dioxide or, more simply, by bubbling air free from carbon dioxide
through the water for 15 minutes. The air is freed from carbon dioxide by passing it over a column
containing pellets of sodium hydroxide.
Store the water in the absence of atmospheric carbon dioxide.
3.1 Barium chloride, dihydrate (Bac 1 .2H2 O), 1 O0 g/l solution.
3.2 Hydrochloric acid, N standard volumetric solution (see Note, section 6).
3.3 Sodium hydroxide, 0.1 N standard volumetric solution (see clause 5.3).
3.4 Phenolphthalein, 10 g/l ethanolic solution. Dissolve 1 g of phenolphthalein in 95 'lo
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