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IS0
I N T ER N AT I O N A L O RG A N I Z AT I ON FOR STAND AR D IZATl O N
IS0 RECOMMENDATION
R 807
CHEMICAL ANALYSIS OF MAGNESIUM AND MAGNESIUM ALLOYS
POLAROGRAPHIC DETERMINATION OF ZINC
(Zinc content between 0.1 and 4 'L)
1st EDITION
August 1968
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belongs to IS0 Member Bodies. Reproduction of these
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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 807, Chemical analysis of magnesium and magnesium alloys -
Polarographic determination of zinc (Zinc content between O. 1 and 4 'la), was drawn up by Technical
Committee lSO/TC 79, Light metals and their alloys, the Secretariat of which is held by the
Association Française de Normalisation (AFNOR).
L,
Work on this question by the Technical Committee began in 1957 and led, in 1965, to the
adoption of a Draft IS0 Recommendation.
In December 1966, this Draft IS0 Recommendation (No. 1128) 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 :
India
Argentina South Africa,
Ireland Rep. of
Austria
Belgium Israel Spain
Switzerland
Brazil Italy
Sweden
Canada Japan
Turkey
Chile Korea, Rep. of
U.A.R.
Czechoslovakia Netherlands
New Zealand U.S.A.
France
Norway U.S.S.R.
Germany
Poland Yugoslavia
Hungary
One Member Body opposed the approval of the Draft :
United Kingdom
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in August 1958, to accept it as an IS0 RECOMMENDATION.
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ISO/R 807-1968 (E
IS0 Recommendation R 807 August 1968
CHEMICAL ANALYSIS OF MAGNESIUM AND MAGNESIUM ALLOYS
POLAROGRAPHIC DETERMINATION OF ZINC
(Zinc content between O. 1 and 4 O!,)
1. SCOPE
This IS0 Recommendation describes a polarographic method for the determination of zinc in mag-
nesium and its alloys which do not contain zirconium.
The method is applicable to the determination of zinc content between 0.1 and 4 O/'.
2. PRINCIPLE
Polarographic determination in an ammonium citrate and ammonium chloride medium at approx-
imately pH 9. Zinc is reduced at about -1.2 volt.
3. REAGENTS
3.1 Ammonium chloride (NH4 C 1).
3.2 hre magnesium (99.99 'IO).
3.3 Hydrochloric acid, d = 1.19 (approximately 12 N).
Citric acid, 400 g per litre.
3.4
Dissolve 40 g of citric acid crystals (H3C6HS0,.H20) in water and make up the volumeto
100 ml.
Ammonia solution,d = 0.90 (approximately 14.4 N).
3.5
3.6 "Suppressor"
3.6.1 Solution ofgum arabic, 10 g per litre.
To 1 g of gum arabic add, in small portions and while stirring, 100 ml of water. Prepare
just before use.
3.6.2 Solution of tylose, 20 g per litre.
To 2 g of tylose (methyl - ethyl cellulose; viscosity 100 centipoises) add, in small portions
and while stirring, 100 ml of water. Do not heat.
3.6.3 Solution of Triton X-IOO, 1 g per litre.
Dissolve 0.1 g of Triton X-100 (p-C8H1,C6H4(0CH2CH2),,OH) in water and make up the
vol ume to 1 O0 ml.
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ISO/R 807-1968 (E)
3.7 Sodium sulphite solution, 200 g per litre.
Dissolve 20 g of anhydrous sodium sulphite (NazS03) in water and make up the volume to
100 mi. Prepare just before use.
3.8 Standard zinc solution, 2 g per litre (1 ml contains 2 mg of zinc).
Dissolve 2 g of very pure zinc in 30 ml of hydrochloric acid (3.3) and add 30 ml of water.
When the dissolution is complete transfer to a 1000 ml volumetric flask and make up to volume
with water.
3.9 Standard zinc solution, 0.5 g per litre
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