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Ref. No. : NO/R 915-1968 (E)
IS
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
IS0 RECOMMENDATION
R 915
SULPHURIC ACID AND OLEUM FOR INDUSTRIAL USE
DETERMINATION OF IRON CONTENT
2,2’-bipyridyl spectrophotometric method
1st EDITION
December 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 915, Sulphuric acid and oleum for industrial use - Determination
of iron content - 2,2’-bipyridyl spectrophotometric 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).
Based on detailed work on this question carried out by the Technical Committee, a Draft IS0
Recommendation was adopted in 1965.
In June 1967, this Draft IS0 Recommendation (No. 1185) 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 :
Austria India Spain
Belgium Iran Switzerland
Brazil Ireland Thailand
Chile Italy Turkey
Cuba Japan U.A.R.
Czechoslovakia Netherlands United Kingdom
France New Zealand U.S.S.R.
Germany Poland Yugoslavia
Romania
Hungary
ICAITI* South Africa, Rep. of
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 December 1968, to accept it as an IS0 RECOMMENDATION.
* Instituto Centroamericano de Investigacidn y Tecnologia Industrial (Costa Rica, Guatemala, Honduras,
Nicaragua, El Salvador, Panama).
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ISO/R 9151968 (E)
December 1968
IS0 Recommendation
SULPHURIC ACID AND OLEUM FOR INDUSTRIAL USE
DETERMINATION OF IRON CONTENT
2,2’-bipjuidyl spectrophotometric method
1. SCOPE
This IS0 Recommendation describes a 2,2’-bipyridyl spectrophotometric method for the determi-
nation of the iron content of sulphuric acid and oleum for industrial use.
2. FIELD OF APPLICATION
The method is applicable to the determination of iron content, expressed as Fe greater than 1 p.p.m.
3. PRINCIPLE
Evaporation of the test portion, taking up by means of hydrochloric acid and reduction of iron
(III) by means of hydroxylammonium chloride.
Formation of an iron (II) 2,2’-bipyridyl complex in a buffered medium (pH value between
4.5 and 6).
Spectrophotometric measurement of the coloured complex at a wavelength of about 522 nm.
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ISO/R 9151968 (E)
4. REAGENTS
Distilled water or water of equivalent purity should be used in the test.
4.1 Hydrochloric acid, approximately N solution.
4.2 Hydroxylammonium chloride, 100 g/l solution.
Dissolve 10 g of hydroxylammonium chloride (NH, OH.HCl) in water and dilute to 100 ml.
4.3 Ammonium acetate, 300 g/l solution.
Dissolve 30 g of ammonium acetate (CH,COONH,) in water and dilute to 100 ml.
4.4 2,2’-bipyridyl, 10 g/l hydrochloric acid solution.
Dissolve 1 g of 2,2’-bipyridyl in 10 ml of approximately N hydrochloric acid solution and
dilute to 100 ml.
4.5 Iron standard solution, containing 2.00 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 (about 2 N) and
transfer quantitatively to a 500 ml one-mark volumetric flask. Dilute to the mark and mix
thoroughly.
1 ml of this standard solution contains 2.00 mg of Fe.
4.6 Iron standard solution, containing 0.20 g/l of Fe.
Transfer 50.0 ml of the iron standard solution (4.5) to a 500 ml one-mark volumetric flask,
add 5 ml of 100 g/l sulphuric acid solution (about 2 N), dilute to the mark and mix thoroughly.
1 ml of this standard solution contains 0.20 mg of Fe.
The solution should be prepared just before use.
4.7 Iron standard solution, containing 0.010 g/l of Fe.
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