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UDC 609.721.3 : 545.82
IS0
I N T ERN AT1 O N A L O R G A N IZATl O N FOR STA N DA RD IZATIO N
IS0 RECOMMENDATION
R 794
CHEMICAL ANALYSIS OF MAGNESIUM AND ITS ALLOYS
PHOTOMETRIC DETERMINATION OF COPPER
(Oxalyldihydrazide method
applicable to copper content between 0.002 and 0.4
1st EDITION
July 1968
COPYRIGHT RESERVED
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 794, Chemical analysis of magnesium and its alloys - Photometric
determination of copper (Oxalyldihydrazide method applicable to copper content between O. 002 and
0.4 ‘lo), was drawn up by Technical Committee iSO/TC 79, Light metals and their alloys, the
Secretariat of which is held by the Association Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1956 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In June 1966, this Draft IS0 Recommendation (No. 967) 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 Korea, Rep. of
Sweden
Austria
India Switzerland
Belgium
Ireland Turkey
Brazil
Israel U.A.R.
Bulgaria Italy
United Kingdom
Canada Netherlands
U.S.A.
Chile Norway
U.S.S.R.
Czechoslovakia Poland Yugoslavia
France South Africa,
Germany Rep. of
Hungary 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 July 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 794-1968 (E)
IS0 Recommendation R 794 July 1968
CHEMICAL ANALYSIS OF MAGNESIUM AND ITS ALLOYS
PHOTOM ETR IC D ETE RM I NAT1 ON OF COPPE R
(Oxalyldihydrazide method
applicable to copper content between 0.002 and 0.4
1. SCOPE
This IS0 Recommendation describes a photometric method for the determination of copper in
1.1
magnesium and its alloys.
The method is applicable to the determination of copper content between 0.002 and 0.4
1.2
The method does not apply to the special case of magnesium alloys containing zirconium. in
1.3
this IS0 Recommendation this special case is not treated.
2. PRINCIPLE
2.1 Attack with hydrochloric acid.
2.2 Formation between pH 8.8 and pH 9.3, in the presence of acetaldehyde, of the violet-coloured
complex, copper-oxalyldihydrazide, the optimum pH range being obtained by adding a
controlled amount of ammonia.
2.3 Photometric measurement at a wavelength of about 540 nm.*
3. REAGENTS
3.1 H-vdrochloric acid, d = 1.19 (approximately 12 N).
Nitric acid, d = 1.23 (approximately 7.4 N).
3.2
Take 50 ml of nitric acid, d = 1.40 (approximately 15 N), and make up the volume to 100 nil
with water.
3.3 Hydrogen peroxide, 36 d = 1.12 (approximately 120 volumes).
3.4 Ammonia solution, d = 0.90 (approximately 14.4 N).
3.5 Citric acid solution, 500 g per litre.
rolume to 1000 ml.
Dissolve 500 g of citric acid (C,H,O,.H,O) in water and make up the
3.6 Acetaldehyde solution, 400 g per litre.
In a 1000~ml volumetric flask place 400 g of acetaldehyde (CH,CHO) and cool to approximately
5 OC; slowly add cooled distilled water (at about 5 OC) and make up the volume to 1000 ml.
(Store at a temperature of about 15 OC).
NOTE. - Since heat is prodiiccd when water and acetaldehyde are mixed, and since acetaldehyde IS very
volatile (boiling point 21 OC), it is recommended that the vessel in which the mixing takes place should be
cooled by cold water.
*
Aluminium is complexed by citric acid. Alloying elements or impurities present in magnesium and its alloys do
not interfere.
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ISO/R 794-1968 (E
Oxalyldihydrazide solution, 2.5 g per litre.
3.7
Dissolve 2.5 g of oxalyldihydrazide (C,H,N,O,) in warm water (40 to 50 OC) and, after
cooling to 20 OC, make up the volume to 1000 ml. Filter if necessary.
3.8 Standard copper solution, 1 g per litre (1 ml contains 1 mg of copper).
3.8.1 In a tall-form beaker of suitable capacity (e.g. 400 mi), dissolve 1 g of electrolytic copper
(not less than 99.95 in 10 ml of nitric acid (3.2) to which 20 ml of water have been
added. Cover with a watch-glass. When completely dissolved, evaporate on a water bath
until crystallization commences. Take up with water, transfer to a 1000 ml volumetric
flask, rinse and after cooling make up the volume to 1000 ml with water.
Alternatively
3.8.2 Dissolve 3.9296 g of copper sulphate crystals (CuS0,.5H,O) in water and make up the
volume to 1000 ml.
3.9 Standard copper solution, 0.05 g per litre (1 ml contains 0.05 mg of copper).
Transfer 50.0 ml of standard copper solution (3.8) to a 1000 ml volumetric flask and make up
the volume to 1000 ml with water.
3.10 Standard copper solution, 0.005 g per litre (1 ml contains 5 pg of copper).
Transfer 50.0 ml of standard copper solution (3.9) to a 500 ml volumetric flask and make up
the volume to 500 ml with water. Prepare just before use.
3.11 Standard copper solution, 0.0025 g per litre (1 ml contains 2.5 pg of copper),
Transfer 50.0 ml of standard copper solution (3.9) to a 1000 ml volumetric flask and make up
the volume to 1000 ml with water. Prepare just before use.
4. APPARATUS
4.1 Ordinary laboratory equipment
All volumetric apparatus should comply with national standards.
4.2 pH meter provided with glass electrode.
4.3 Electrophotometer or spectrophotometer (wavelength about 540 nm).
5. SAMPLING
5.1 Laboratory sample
See the appropriate national standard on sampling.
5.2 Test sample
Chips not more than 1 mm thick should be obtained from the laboratory sample by drilling or
milling.
6. PROCEDURE
6.1 Caiibration graph
6.1.1 Solution in hydrochloric acid. In a 250 ml beaker, place 20 ml of hydrochloric acid (3.1)
and 1 ml of hydrogen peroxide (3.3), then evaporate the liquid almost completely. Add
50 ml of water, bring to the boil and keep boiling for about 5 minutes, cool and transfer
to a 200 ml volumetric flask. Make up the volume to 200 ml with water.
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