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IS0
STA N DA R D I ZATl O N
I NT ERN AT1 O N A L O RG A N IZ AT1 O N FO R
IS0 RECOMMENDATION
R 619
METHODS OF CHEMICAL ANALYSIS OF MANGANESE ORES
DETERMINATION OF CHROMIUM CONTENT
1st EDITION
September 1967
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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 619, Methods of Chemical Analysis of Manganese Ores -
Determination of Chromium Content, was drawn up by Technical Committee ISO/TC 65, Man-
ganese Ores, the Secretariat of which is held by Komitet Standartov Mer i Izmeritel’nyh Priborov
pri Sovete Ministrov S.S.S.R. (GOST).
Work on this question by the Technical Committee began in 1954 and led, in 1964, to the
adoption of a Draft IS0 Recommendation.
In April 1965, this Draft IS0 Recommendation (No. 778) 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 Hungary Spain
Austria India Switzerland
Chile Italy Turkey
Czechoslovakia Korea, Rep. of U.A.R.
France Netherlands United Kingdom
Germany Poland U.S.S.R.
Greece Romania Yugoslavia
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 September 1967, to accept it as an IS0 RECOMMENDATION.
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ISO/R 619 - 1967 (E)
IS0 Recommendation R 619 Sep te m be r 1 967
METHODS OF CHEMICAL ANALYSIS OF MANGANESE ORES
DETERMINATION OF CHROMIUM CONTENT
(Atomic mass Cr: 52.01; molecular mass Cr,O,: 152.02)
This IS0 Recommendation contains three parts :
I. Introduction . section 1
II. Photometric method of determination of chromium content by using
diphenylcarbazide. . sections 2 to 5
III. Volumetric method of determination of chromium content by using
silver persulphate . sections 6 to 9
I. INTRODUCTION
1. GENERAL INSTRUCTIONS
1.1 In the following analysis use a sample for chemical analysis of air-dried manganese ore,
sampled and prepared in accordance with IS0 Recommendation R 309, Methods of Sampling
Manganese Ores.
Simultaneously with the collection of test samples for the determination of chromium, take
three more test samples for the determination of hygroscopic moisture.
Calculate the content of chromium in ore on the dry basis by multiplying the numerical
results of the determination of chromium by the conversion factor Ky as found from the
following formula :
1 O0
K= -
100-A
where
A is the percentage hygroscopic moisture content.
1.2
The determination of chromium in manganese ore should be carried out by analysing three
parallel-weighed test samples of the ore together with two blank tests to allow the necessary
corrections to be made to the results of the determination.
Simultaneously and under the same conditions, carry out a check analysis of a standard
sample of manganese ore for the determination of its chromium content. The standard
sample for analysis should be taken from the same type of ore as that from which the analysed
sample was taken.
The arithmetical mean of the three results should be accepted as the final result.
The following conditions should be observed:
The difference between the highest and the lowest results should not exceed double
the absolute value of the permissible tolerance for the corresponding interval of
5.2 and 10.2, “Accuracy of
chromium content shown in the Tables under clauses
method”.
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ISO/R 619 - 1967 (E)
The average result of the simultaneous check analysis of the standard sample of
manganese ore for chromium content should not differ from the result shown in the
certificate by more than the & value of the permissible tolerance for the correspond-
ing interval of chromium content shown in the tables under clauses 5.2 and 10.2,
“Accuracy of method”.
1.3 The test samples should be weighed to an accuracy of i 0.0002 g.
1.4 Double distilled or de-ionized water should be used during the procedure and for prepar-
ation of the solutions.
1.5 Meanings of particular expressions :
implies a temperature of the liquid of 60 to
hot water (or solution)
70 OC;
warm water (or solution) implies a temperature of the liquid of 40 to
50 OC;
1: 1, 1: 2, 1: 5, etc. the first figure gives the number of parts by
diluted
volume of concentrated acid or some other
solution ;
the second figure gives the number of parts by
volume of water.
1.6 Indications as to the concentrations of solutions show the quantity of solute, in grammes,
in the corresponding volume of the solvent.
1.7 The following abbreviations and symbols are used:
CP chemically pure
d relative density
g gramme
g/1 grammes per litre
1 litre
ml millilitre
nm nanometre
N standard solution of normal concentration
PFA pure for analysis.
II. PHOTOMETRIC METHOD OF DETERMINATION OF CHROMIUM CONTENT
BY USING DIPHENYLCARBAZIDE
(For chromium content below 0.1 %)
2. PRINCIPLE OF METHOD
A test sample of ore is fused with sodium carbonate and sodium peroxide and the fused mass is
extracted in water.*
Chromium is determined in the solution by the photometric method based on the oxidation of
diphenylcarbazide with chromate ions with the formation of a compound of red-violet colour.
* If the vanadium content exceeds 0.1 %, its effect can be eliminated by extraction of 8-hydroxyquinolate of vanadium with
chloroform (see the Note under clause 4.4).
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ISO/R 619 - 1967 (E)
3. REAGENTS
3.1 Potassium dichromate, CP.
3.2 Sodium carbonate, CP, anhydrous.
3.3 Sodium peroxide, CP.
3.4 Ethanol, PFA.
3.5 Chloroform, CP.
3.6 Sulphuric acid, CP (6N).
3.7 Sulphuric acid, CP (2N).
3.8 Acetic acid, 80%.
3.9 Acetic acid, 2N.
3.10 Ammonium persulphate (NH4)2S,0,, CP, aqueous solution (250 g/l), freshly prepared.
3.11 Diphenylcarbazide, CP, freshly prepared solution; O. I g of diphenylcarbazide is dissolved in
10 ml of acetic acid (3.8) and diluted with water to 100 ml.
3.12 8-h~1droxyquinoline, CP, solution (25 g/l) in acetic acid (3.9).
3.13 Silver sulphate Ag,SO,, CP, aqueous solution (2.5 g/l).
3.14 Standard solution of chromium. Dissolve 0.2828 g of potassium dichromate, CP, (3.1),
recrystallized and dried at a temperature of 180 to 200°C, in a small quantity of water in a
1 litre volumetric flask, dilute with water up to the mark and stir; 1 ml of the solution con-
tains 0.0001 g of chromium.
3.15 Methyl-orange, aqueous solution (1 g/l).
4. PROCEDURE
4.1 Weigh accurately about 1 g of the manganese ore into a nicA or corundum crucible, ad
8 g of sodium carbonate (3.2) and sodium peroxide (3.3) mixture (1: 1), mix thoroughly,
cover the crucible with a lid and fuse the mixture in a muffle furnace at a temperature of
700 to 800 "C for 15 to 20 minutes.
4.2 After the fused mass has cooled, extract it in 200 ml of hot water, heat the solution to
boiling, allow to boil for 15 to 20 minutes, add ethanol (3.4) drop by drop and boil until the
green colouring disappears.
4.3 After cooling the solution, transfer it with the precipitate to a 250 ml volumetric flask,
dilute with water to the mark and mix; allow the residue to settle and filter the solution
through a dry filter into a dry beaker, rejecting the first 10 to 15 ml of filtrate.
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ISO/R 619 - 1967 (E)
4.4 Transfer a 10 ml aliquot portion of the filtrate into a 100 ml beaker, neutralize with 2N
sulphuric acid solution (3.7) in the presence of methyl-orange (3.15) until the yellow colour
changes to orange and mix for 2 minutes.
NOTE. - When vanadium content exceeds 0,1% place the aliquot part after the process of neutralization
into a 100 ml separating funnel, add 0.2 to 0.3 ml of the acetic acid solution of 8-hydroxyquinoline (3.12)
and 3
to 5 ml of chloroform (3.5), shake vigorously for 1 to 2 minutes and allow to settle for 2 to 3 minutes.
off the chloroform layer into a separate vessel and discard.
Drain Repeat the extraction with chloroform 2 to
3 times in order to ensure a more complete extraction of vanadium hydroxyquinolate. The extraction being
completed, the solution, containing chromium, is filtered through a filter wetted with water. Wash the
filter 5 or 6 times with warm water and resume the determination, starting with clause 4.5.
4.5 Add 2 ml of sulphuric acid (3.6) and 4 ml of silver sulphate solution (3.13) to the solution
and heat to boiling.
Add 2 ml of ammonium persulphate solution (3.10) to the boiling solution and continue
boiling for 10 minutes. Cool the solution, transfer it to a 50 ml volumetric flask, add
5 ml of the diphenylcarbazide solution (3.ll), mix for 20 to 30 seconds, dilute with water
to the mark, mix again and carry out the photometric determination with a green light
filter (wave-length 520 to 530 nm). If vanadium is present the photometry should be
carried out in IO to 15 minutes.
4.6 Simultaneously take t
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