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UDC 661.833.622 : 620.1
IS0
FOR S TA N D A R D 1 ZATl O N
I N T E R N AT I ON A L O R G A N I Z AT 1 O N
IS0 RECOMMENDATION
R 742
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF CHLORIDE CONTENT
VOLHARD 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 742, Sodium carbonate for industrial use - Determination of
chloride content - Volhard volumetric method, was drawn up by Technical Committee ISOlTC 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. 1008) 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 Italy Switzerland
Austria Japan Turkey
Korea, Rep. of U.A.R.
Belgium
Netherlands United Kingdom
Brazil
Chile New Zealand U.S.A.
Czechoslovakia Poland U.S.S.R.
France Portugal Yugoslavia
Germany Romania
Hungary South Africa,
Rep. of
India
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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ISO/R 742-1968 (E)
IS0 Recommendation R 742 May 1968
SODIUM CARBONATE FOR I.NDUSTRIAL USE
DETERMINATION OF CHLORIDE CONTENT
VOLHARD VOLUMETRIC METHOD
1. SCOPE
This IS0 Recommendation describes the Volhard volumetric method for the determination of
chloride content.
2. FIELD OF APPLICATION
The method is applicable to the determination of chlorides in sodium carbonate for industrial use
for contents higher than 0.05 (m/m) expressed as sodium chloride.
2.1 Special case
Determination of chloride contents equal to or lower than 0.05 (m/m) expressed as sodium
chloride (see section 8).
3. PRINCIPLE
Precipitation of C1- ions by addition of excess of silver nitrate and titration of the excess with
(III) sulphate.
ammonium thiocyanate in the presence of ammonium-iron
4. REAGENTS
Distilled water or water of equivalent purity should be used in the test.
4.1 Nitric acid, d = 1.4 approximately, 68 (m/m) or approximately 14 N solution.
4.2 Nitric acid, approximately 0.2 N solution.
4.3 Silver nitrute, 0.1 N standard volumetric solution (see Note, section 7).
4.4 Ammonium thiocyanate, 0.1 N standard volumetric solution (see Note, section 7).
4.5 Ammonium-iron (III) sulphate, nitric solution. Dissolve 25 g of ammonium-iron (III) sulphate
hydrate [ (NH,),S04.Fe,(S04),.24H,0] in 100 ml of water. Add 50 ml of nitric acid,
d = 1.4 approximately, and mix thoroughly.
4.6 Litmus paper.
5. APPARATUS
Ordinary laboratory apparatus.
6. PROCEDURE
6.1 Test portion
Weigh to the nearest 0.01 g, 10 5 0.1 g of the test sample.*
*
See IS0 Recommendation R 739, Sodium carbonate for indusirial use - Preparation and storage of test mmples.
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ISO/R 742-1968 (E)
6.2 Preparation of test solution
Dissolve the test portion by pouring it in smai1,quantities at a timc into a 500 ml conical flask
containing approximately 100 ml of water. Stir during the operation. Neutralize with the nitric
acid solution (4.1) in the presence of the litmus paper (4.6). Then add 0.5 to 1 ml excess of the
nitric acid solution (4.1) and cool under running water to room temperature.
6.3 Titration
Add approximately 3 ml of the nitric solution of ammonium-iron (111) sulphate (4.5) to the
test solution.
a burette with the standard volumetric solution of si
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