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UDC 669.71.3 : 545.82
IS0
I N T E R N AT I ON A L O R G A N I2 AT I ON FOR S TA N DARD I ZAT I O N
IS O R ECO M M EN DATI O N
R 795
CHEMICAL ANALYSIS OF ALUMINIUM AND ITS ALLOYS
PHOTOMETRIC DETERMINATION OF COPPER
(Oxalyldihydrazide method
applicable to copper content between 0.002 and 0.8
1 st E DIT1 ON
July 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 795, Chemical analysis of aluminium and its alloys - Photometric
determination of copper (Oxalyldihydrazide method applicable to copper content between O. O02 and
0.8 %, was drawn up by Technical Committee ISO/TC 79, Light metals and their alloys, the Secretar-
iat 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. 968) was circulated to all the IS0 Member
Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by the fol-
lowing Member Bodies :
Argentina
Korea, Rep. of Sweden
Austria
India Switzerland
Belgium Ireland Turkey
Brazil Israel U.A.R.
Bulgaria
Italy U.S.A.
Canada Netherlands
U. S. S. R .
Chile
Norway Yugoslovia
Czechoslovakia Poland
France South Africa,
Germany Rep. of
Hungary Spain
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 July 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 795-1968 (E)
IS0 Recommendation R 795 July 1968
CHEMICAL ANALYSIS OF ALUMINIUM AND ITS ALLOYS
PHOTOMETRIC DETERMINATION OF COPPER
(Oxalyldihydrazide method
applicable to copper content between 0.002 and 0.8 '6)
1. SCOPE
1.1 This IS0 Recommendation describes a photometric method for the determination of copper in
aluminium and its alloys.
1.2 The method is applicable to the determination of copper content between 0.002 and 0.8
1.3 The method does not apply completely to the special case of alloys with silicon contents exceed-
ing 1 for which it should be modified as described in the Annex.
2. PRINCIPLE
2.1 Attack with hydrochloric acid.
2.2 Formation between pH 9.1 and pH 9.5, in the presence of acetaldehyde, of the violet-coloured
complex, copper-oxalyldihydrazide, the optimum pH range being obtained by adding a control-
led amount of ammonia.
Photometric measurement at a wavelength of about 540 nm.*
2.3
3. REAGENTS
3.1 Hydrochloric acid, d = 1.19 (approximately 12 N).
3.2 Hydrofluoric acid, 40 d = approximately 1.15.
3.3 Nim'c acid, d = 1.23 (approximately 7.4 N).
Take 50 ml of nitric acid, d = 1.40 (approximately 15 N), and make up the volume to 1 O0 ml
with water.
3.4 Sulphuric acid, d = 1.48 (approximately 17.5 N).
Cautiously pour 50 ml of sulphuric acid, d = 1,84 (approximately 35.6 N), into water and after
cooling make up the volume to 1 O0 ml.
Hydrogen peroxide, 36 d = 1.12 (approximately 120 volumes).
35
3.6 Ammonia solution, d = 0.90 (approximately 14.4 N).
Cim.c acid solution, 500 g per litre.
3.7
Dissolve 500 g of citric acid (C,H,O,.H,O) in water and make up the volume to 1000 ml.
3.8 Acetaldehyde solution, 400 g per litre.
In a 1000 ml volumetric flask place 400 g of acetaldehyde (CH,CHO), 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 produced 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 aluminium and its alloys do
not interfere.
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ISO/R 795-1968 (E)
3.9 Oxalyldihydrazide solution, 2.5 g per litre.
Dissolve 2.5 gof 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.
3.10 Standard copper solution, 1 g per litre (1 ml contains 1 mg of copper).
3.10.1 In a tall-form beaker of suitable capacity (e.g. 400 mi), dissolve 1 g of electrolytic copper
(not less than 99.95 O/') in 10 ml of nitric acid (3.3) to which 20 ml of water have been added.
Cover with a watch-glass. When completely dissolved, evaporate on a water bath until crystal-
lization commences. Take up with water, transfer to a 1000 ml volumetric flask, rinse and
after cooling make up the volume to 1000 ml with wter.
Alternatively
3.10.2 Dissolve 3.9296 g of copper sulphate crystals (CuSO,. 5H2 O) in water and make up the vol-
ume to 1000 ml.
3.1 I Standard copper solution, 0.05 g per litre (1 ml contains 0.05 mg of copper).
Transfer 50.0 ml of standard copper solution (3.10) to a 1000 ml volumetric flask and make up
the volume to 1000 ml with water.
3.12 Standard copper solution, 0.005 g per litre (1 ml contains 5 pg of copper).
Transfer 50.0 ml of standard copper solution (3.1 1) to a 500 ml volumetric flask and make up
the volume to 500 ml with water. Prepare just before use.
3.13 Standard copper solution, 0.0025 g per litre (1 ml contains 2.5 pg of copper).
Transfer 50.0 ml of standard copper solution (3.1 1) 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 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 Calibration graph
6.1.1 Solution in hydrochloric acid. In a 250 ml beaker, place 30 ml of hydrochloric acid (3.1) and
1 ml of hydrogen peroxide (3.9, 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.
6.1.2 Preliminary testforadjustingthepHvalue. In a beaker of suitable capacity (e.g. 50 to 100 ml)
place 10 ml of hydrochloric acid solution (6.1.1), 10 ml of standard copper solution (3.12)
and 2 ml of citric acid solution (3.7); mix and add 10 ml of acetaldehyde solution (3.8).
By means of a graduated pipette or burette, add sufficient ammonia solution (3.6), while
stirring, to bring the pH of the solution to about 9.3 (within the range 9.1 to 9.5).
Note the number of millilitres of ammonia solution used for adjusting the pH value (the
amount will be about 7 to 9 mi). Discard this test solution.
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ISO/R 795-1968 (E
6.1.3 Plotting of the calibration graph. In each of a series of nine 50 ml volumetric flasks, place
10 ml of hydrochloric acid (3.1), then respect
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