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UDC 669.71.3 : 545.3
IS0
I N T E RN AT I O N A L ORGANIZATION FOR STA N DA RD IZATl O N
IS0 RECO M M EN DATION
R 796
CHEMICAL ANALYSIS OF ALUMINIUM AND ITS ALLOYS
ELECTROLYTIC DETERMINATION OF COPPER
IN ALUMINIUM ALLOYS
(Copper content greater than or equal to 0.50 O/')
1 st E DIT I 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 obtain4 through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 796, Chemical analysis of aluminium and its alloys - Electrolytic
determination of copper in aluminium alloys (Copper content greater than or equal to 0.50 YJ, 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. 969) 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 :
Ar gent in a Hungary South Africa,
Austria Korea, Rep. of Rep. of
Belgium India Spain
Brazil Ireland Sweden
Bu 1 g a r i a Israel Switzerland
Canada Italy Turkey
Chile
Japan U.A.R.
Czechoslovakia
Netherlands United Kingdom
France
Norway U.S.S.R.
Germany Poland
Yugoslavia
One Member Body opposed the approval of the Draft :
U.S.A.
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 7% - 1968 (E
IS0 Recommendation R 796 July 1968
CHEMICAL ANALYSIS OF ALUMINIUM AND ITS ALLOYS
ELECTROLYTIC DETERMINATION OF COPPER
IN ALUMINIUM ALLOYS
(Copper content greater than or equal to 0.50 'I!,)
1. SCOPE
1.1 This IS0 Recommendation describes an electrolytic method for the determination of copper
in aluminium alloys.
1.2 The method is applicable to the determination of copper content greater than or equal to
0.50 'Io.
1.3
The method does not apply completely to the following special cases for which it should be
modified as described in Annex A and Annex B :
alloys containing tin or antimony (see Annex A);
(a)
alloys containing bismuth (see Annex B).
(b)
2. PRINCIPLE
2.1 Attack with a mixture of perchloric acid and nitric acid.
2.2 Dehydration of the silica in a perchloric medium and filtration of the insoluble residue.
2.3 Volatilization of the siliceous residue and recovery of copper from the residue.
2.4 Electrolysis of the solution after addition of nitric acid.
3. REAGENTS
3.1 Ethanol, 95 'Io, d = approximately 0.816.
Sulphamic acid (NH,SO,H).
3.2
3.3 Hydrobromic acid, 48 'la, d = approximately 1.49.
3.4 Hydrochloric acid, d = 1.1 (approximately 6 N).
Take 500 ml of hydrochloric acid, d = 1.19 (approximately 12 N), and make up the volume to
1000 ml with water.
3.5 Hydrofluoric acid, 40 'k, d = approximately 1.1 5.
3.6 Nitric acid, d = 1.40 (approximately 15 N).
3.7 Nitric acid, d = 1.23 (approximately 7.4 N).
Take 500 mi of nitric acid, d = 1.40, and make up the volume to 1000 ml with water.
3.8 Perchloric acid, d = 1.67 (approximately 1 1.7 N).
(Perchloric acid, d = 1.54 (approximately 9 N), can also be used. loo0 ml of perchloric acid,
d = 1.67, is equivalent to 1270 ml of perchloric acid, d = 1.54).
3.9 Perchloric acid, d = 1.33 (approximately 5.8 N).
Take 500 ml of perchloric acid, d = 1.67, and make up the volume to 1000 ml with water.
3.10 Sulphuric acid, d = 1.33 (approximately 1 1.7 N).
Carefully add 35 mi of sulphuric acid, d = 1.84, to water and, after cooling, make up the
volume to 100 mi.
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ISO/R 7% - 1968 (I
3.11 Tartaric acid solution, 300 g per litre.
Dissolve 300 g of tartaric acid (C,H, O,) in a little water and make up the volume to 1000 ml.
Ammonia solution, d = 0.95 (approximately 7 N).
3.12
Take 500 ml of ammonia solution, d = 0.90 (approximately 14.4 N), and make up the volume
to 1000 ml with water.
3.13 Bromine water, saturated solution.
Formic mixture :
3.14
Formic acid, d = 1.20 (approximately 24 N)
20ml madeup to
Ammonia solution, d = 0.90 (approximately 14.4 N)
3 ml 3 100 ml with water
Dilute 20 ml of formic acid (HCOOH) with about 50 ml of wtmter, add 3 ml of ammonia
solution and make up the volume to 100 ml with water.
3.15 Formic mixture wash solution.
Dilute 25 ml of formic mixture (3.14) to 1000 ml with water, heat to 50 to 60 "C and saturate
with hydrogen sulphide. Prepare just before use.
3.16 Methyl red solution.
Dissolve 0.10 g of methyl red in 100 ml of ethanol, 95 'Io (3.1).
4. APPARATUS
4.1 Ordinaly laboratory equipment
All volumetric apparatus should comply with national standards.
4.2 Laboratory electrolyser fitted with a device for stirring the electrolyte (e.g. a rotating anode
or a magnetic stirrer).
4.3 Cylindrical platinum-iridium wire gauze cathode (Winkler electrode).
4.4 Platinum-iridium anode (spiral, or gauze, etc.).
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 Test portion
Weigh the test portion with an accuracy of k 0.001 g, in accordance with the quantities shown
in Table 1, below.
6.2 Determination
6.2.1 Attack of the test portion. Depending on the assumed copper content, take the size of test
portion shown in Table 1 and use the corresponding quantities of the reagents.
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ISO/R 796 - 1968 (E
TABLE 1
Assumed copper Volume of perchloric Volume of nitric
Mass of test portion
content acid 5.8 N (3.9) 1 acid 15 N (3.6) 1
I I I
rnl ml
Place the test portion in a suitable vessel (porcelain basin or beaker). Just before use, mix
the appropriate quantities of perchloric acid (3.9) and nitric acid (3.6) and add a small
portion of this nitroperchloric mixture to the test portion. Cover the vessel with a watch-
glass, heat moderately in order to start the reaction and then stop heating immediately.
Cautiously add the remainder of the nitroperchloric mixture in small portions. cooling as
required.
If the test portion is difficult to attack, add a few drops of hydrochloric acid (3.4). When
the attack is complete, evaporate to copious white fumes of perchloric acid, avoiding
spattering, and continue evaporating and fuming for 15 to 20 minutes. Allow to cool and
add approximately 200 to 400 ml of boiling water, depending on the size of the test portion.
Stir and boil for about 5 minutes.
6.2.2 Filtration and washing. Allow the residue to settle while hot (40 to 60 OC), then filter
through a medium texture filter containing a little paper-pulp. Carefully wash the vessel,
the residue and the fiter with boiling water, collecting the fdtrate and the washings in a
suitable vessel (e.g. a 400 to 1 O00 ml beaker).
NOIL. Washing should be thorough because any perchloric acid retained by the silica niight lead to
spattering during incineration of the filter paper.
6.2.3 Recovery of copper from the residue. Place the fiter and the residue in a platinum vessel;
dry at 110 to 120 OC in a hot-air oven, then incinerate carefully at 500 to 600 "C until
combustion of the filter is complete, taking care that the fiter paper does not burst into
flames (to avoid loss of copper). Allow to cool, add 1 ml of sulphuric acid (3.10), 2 to 5 ml
of hydrofluoric acid (3.5), then nitric acid (3.7), dropwise, until the solution becomes
perfectly clear. Evaporate to dryness without calcining and take up the residue with a little
hot water and about 1 ml of perchloric acid (3.9). Dissolve by heating, fiter if necessary,
and add the solution obtained to the main solution.
6.2.4 Electrolysis. Adjust the volume of the solution to about 200 to 300 ml, add 6 to 10 ml of
nitric acid (3.7) and approximately 1 g of sulphamic acid (3.
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