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IS0
I NTERN AT1 ON A L O R G A N 1 ZATl ON
FO R STA N DA RD 1 ZATl ON
IS0 RECOMMENDATION
R 744
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF IRON CONTENT
2,2' - BlPYRlDYL PHOTOMETRIC METHOD
1st EDITION
May 1968
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by the national standards organization of that country, being
of ISO.
a member
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 744, Sodium carbonate for industrial use - Determination of
iron content - 2,2' - bipyndyl photometric method, was drawn up by Technical Committee
ISO/TC 47, Chemistry, the Secretariat of which is held by the Ente Nazionale Italian0 di Unifi-
cazione (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. 1010) 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
Belgium Korea, Rep. of U.A.R.
Brazil Netherlands United Kingdom
Chile New Zealand U.S.A.
Czechoslovakia
Poland U.S.S.R.
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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I
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ISO/R 744 -1968 (I
IS0 Recommendation R 744 May 1968
SODIUM CARBONATE FOR INDUSTRIAL USE
DETERMINATION OF IRON CONTENT
2,2' - BIPYRIDYL PHOTOMETRIC METHOD
1. SCOPE
This IS0 Recommendation describes the 2,2' -bipyridyl photometric method for the determination
of the iron content of sodium carbonate for industrial use.
2. PRINCIPLE
Preliminary reduction of trivalent iron by means of hydroxylammonium chloride.
Formation of a bivalent iron - 2,2'-bipyridyl complex in the presence of ammonium acetate.
Photometric measurement of the coloured complex at a wavelength of about 522 nm.
3. REAGENTS
Distilled water or water of equivalent purity should be used in the test.
3.1 Hydrochloric acid, d = 1.8 approximately, 37 oL (m/m) or approximately 12 N solution.
3.2 Hydrochloric acid, approximately N solution.
3.3 Hydroxylamrnonium chloride, 1 O0 g/l solution. Dissolve 1 O g of hydroxylammonium chloride
(",OH . HCl) in water and dilute to 100 ml.
Ammonium acetate, 200 g/l solution. Ammonium acetate used for the solution should have an
3.4
iron content not higher than 1 ppm.
3.5
2,2'-bipyridyl, 1 g/l hydrochloric acid solution. Dissolve 1 g of 2,2'-bipyridyl, weighed to the
nearest 0.2 mg, in 20 ml of the hydrochloric acid solution (3.2) and dilute to 1000 ml.
3.6 Iron standard solution containing 2 g/l of Fe. Weigh to the nearest 1 mg, 7.022 g of iron (II)
.
ammonium sulphate hexahydrate and place in a beaker of suitable capacity. Add 50 ml of
100 g/l sulphuric acid solution, transfer to a 500 ml one-mark volumetric flask and wash.
Dilute to the mark. 1 ml of this standard solution contains 2 mg of Fe.
3.7 Iron standard solution containing 0.2 g/l of Fe. Transfer 50.0 ml of the iron standard solution
(3.6) to a 500 ml one-mark volumetric flask, add 5 mi of 100 g/i sulphuric acid solution and
dilute to the mark. 1 ml of this standard solution contains 0.2 mg of Fe. The solution should be
prepared just before use.
3.8 Iron standard solution containing 0.01 g/l of Fe. Transfer 50.0 ml of the iron standard solution
(3.7) to a 1000 ml one-mark volumetric flask and dilute to the mark. 1 ml of this standard
solution contains 1 O pg of Fe. The solution should be prepared just before use.
3.9 Iron standard solution containing 0.002 g/l of Fe. Transfer 50.0 ml of the iron standard
solution (3.8) to a 250 ml one-mark volumetric flask and dilute to the mark. 1 ml of this
standard solution contains 2 pg of Fe. The solution should be prepared just before use.
3.10 L iîmus-paper.
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ISO/R 744-1968 (E
4. APPARATUS
Ordinary laboratory apparatus.
4.1 Spectrophotometer,
or
4.2 Photoelectric absorptiometer.
5. PROCEDURE
5. I Test portion
Weigh to the nearest 0.1 g, 50 I 1 g of the test sample.*
5.2 Blank test
Place a volume of the hydrochloric ac
...