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IS0
I N T ER N AT I O N A L ORGAN 12 AT I ON FOR STAND AR D IZATl ON
IS0 RECO M M EN DATI O N
R 743
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF SULPHATE CONTENT
BARIUM SULPHATE GRAVIMETRIC METHOD
1st EDITION
May 1968
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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 743, Sodium carbonate for industrial use - Determination of
sulphate content - Barium sulphate gravimetric method, was drawn up by Technical Committee
ISO/TC 47 - Chemistry, the Secretariat of which is held by the Ente Nazionale Italian0 di
Unificazione (UNI).
Work on this question by the Technical Committee began in 1951 and led, in 1956, to the
adoption of a Draft IS0 Recommendation.
In June 1966, this Draft IS0 Recommendation (No. 1009) was circulated to all the IS0 Member
Bodies for enquiry. It was approve'd, 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.A.
Poland U.S.S.R.
Czechoslovakia
France Portugal Yugoslavia
Germany Romania
Hungary South Africa,
India Rep. of
Israel Spain
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 May 1968, to accept it as an IS0 RECOMMENDATION.
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KO/R 743-1968 (E
IS0 Recommendation R 743 May 1968-
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF SULPHATE CONTENT
BARIUM SULPHATE GRAVIMETRIC METHOD
1. SCOPE
This IS0 Recommendation describes a gravimetric method for the determination of the sulphate
content of sodium carbonate for industrial use.
2. PRINCIPLE
Precipitation of SO, *- ions as barium sulphate in diluted hydrochloric acid medium.
Separation of the precipitate obtained; ignition at a temperature of 800 "C and weighing.
3. REAGENTS
Distilled water or water of equivalent purity should be used in the test.
3.1 Hydrochloric acid, d = 1.18 approximately, 37 (m/m) or approximately 12 N solution.
3.2 Sulphuric acid, d = 1.84 approximately, 93.6 (m/m) or approximately 35 N solution.
3.3 Ammonia, d = 0.91 approximately, 25 (m/m) or approximately 15 N solution.
3.4 Barium chloride dihydrate (Bac1 .2H2 O), 100 g/l solution.
3.5 Silver nitrate, 5 g/l nitric solution. Dissolve 0.5 g of silver nitrate in a small amount of water,
add I O ml of nitric acid approximately d = 1.4 and dilute to 1 O0 ml.
3.6
Methyl orange, 0.5 g/l solution. Dissolve 0.05 g of methyl orange in water and dilute to 100 ml.
4. APPARATUS
Ordinary laboratory apparatus and
Platinum crucible, approximately 30 mm top diameter and 30 mm deep.
4.1
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