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IS0
I N T ERN AT I O N A L O R G A N I Z AT I O N FOR STAN DARD IZATl O N
IS0 RECOMMENDATION
L
R 713
CHEMICAL ANALYSIS OF ZINC
POLAROGRAPHIC DETERMINATION OF LEAD AND CADMIUM
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 counm 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 713, Chemical analysis of zinc - Polarographic determination of
lead and cadmium, was drawn up by Technical Committee ISO/TC 18, Zinc and zinc alioys, the
Secretariat of which is held by the Institut Belge de Normalisation (IBN).
Work on this question by the Technical Committee began in 1963 and led, in 1965, to the
adoption of a Draft IS0 Recommendation.
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In September 1966, this Draft IS0 Recommendation (No. 992) 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 :
Switzerland
Argentina Ireland
Italy Thailand
Belgium
Brazil Japan Turkey
Canada Korea, Rep. of U.A.R.
Chile Korea, D.P. Rep. of United Kingdom
Czechoslovakia New Zealand U.S.A.
U.S.S.R.
France Norway
Yugoslavia
Germany South Africa,
Rep. of
Hungary
India Spain
One Member Body opposed the approval of the Draft :
Australia
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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 713-1968(E)
IS0 Recommendation R 713 May 1968
CHEMICAL ANALYSIS OF ZINC
POLAROGRAPHIC DETERMINATION OF LEAD AND CADMIUM
1. SCOPE
This IS0 Recommendation describes a polarographic method for the simultaneous determination of
lead and cadmium in zinc.
The method applies to the following types of zinc : Zn 99.995, Zn 99.99 and Zn 99.95,* defined in
IS0 Recommendation R 752, Zinc ingots.
It is suitable for the determination of lead and cadmium contents between 0.001 ahd 0.05
2. PRINCIPLE OF THE METHOD
Simultaneous polarographic determination of lead and cadmium in a very slightly acid chloride
medium.
3. REAGENTS
Ail reagents should be of analytical reagent grade.
Distilled or demineralized water should be used for preparing solutions and during the actual deter-
mination.
3.1 Inert gas, oxygen-free.
3.2 Hydrochloric acid (d = 1.19), free from lead and cadmium.
Check the purity by the following test :
3.2.1 Take three 5 g test portions of Zn 99.995 zinc or Zn 99.99 zinc for die castings.
3.2.2 Attack the first and second test portion with 35 to 40 ml of hydrochloric acid (3.2), as
indicated under clause 6.3 starting at clause 6.3.2.
3.2.3 To the second test portion, add 1 ml of the standard solution (3.9).
3.2.4 Attack the third test portion with 100 ml of hydrochloric acid (3.2).
3.2.5 The acid is suitable for use if the differences in step heights between the first and third test
portions are less than those between the first and second test portions. If these conditions
are satisfied the volume of acid used for the dissolution contains less than 0.005 mg of lead
and less than 0.005 mg of cadmium.
3.3 Hydrogen peroxide, 30 H, O, (mlm)
3.4 Niîric acid (d = 1.3 to 1.4).
3.5 Hydroxylammonium chloride
3.6 Nickel chloride solution containing 2 g of NiCl,. 6H, O per litre.
*
Although these types of zinc do not normally contain any thallium or indium, these two elements, if present,
can interfere in this determination.
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ISO/R 713-1968 (E
3.7 Standard solution of lead and cadmium No. 1
In a 100 ml beaker, place 0.5 g of pure lead and 0.5 g of pure cadmium, weighed with an
accuracy of f 0.001 g. Cover with approximately 10 ml of water and dissolve with about 5 ml
of nitric acid (3.4). Drive off the nitrous fumes. Cool. Transfer quantitatively into a 500 mi
volumetric flask. Make up the volume to 500 ml with water. Mix. 1 ml of the solution
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