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STANDARD
First edition
1992-l 2-l 5
Iron ores - Determination of calcium content -
Flame atomic absorption spectrometric method
Minerais de fer - Dosage du calcium - M6fhode par spectrom~trie
d’absorption atomique dans la flamme
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Reference number
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IS0 10203: 1992(E)
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IS0 10203:1992(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with ISO, also take part in the
work. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of eiectrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an Inter-
national Standard requires approval by at least 75 % of the member
bodies casting a vote.
International Standard IS0 10203 was prepared by Technical Committee
ISO/TC 102, Iron ores, Sub-Committee SC 2, Chemical analysis.
IS0 10203 and IS0 10204 cancel and replace IS0 4692:1980, of which
they constitute a technical revision.
Annex A forms an integral part of this International Standard. Annexes
B and C are for information only.
0 IS0 1992
All rights reserved. No part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without
permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Genitve 20 l Switzerland
Printed in Switzerland
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IS0 10203:1992(E)
INTERNATIONAL STANDARD
Iron ores - Determination of calcium content - Flame atomic
absorption spectrometric method
1 Scope 3 Principle
Decomposition of the test portion by treatment with
This International Standard specifies a flame atomic
hydrochloric acid and a small amount of nitric acid.
absorption spectrometric method for the determi-
nation of the calcium content of iron ores.
Evaporation to dehydrate silica, followed by dilution
and filtration.
This method is applicable to calcium contents be-
tween 0,Ol % (m/m) and IO,0 % (m/m) in natural
Ignition of the residue and removal of silica by
iron ores, iron ore concentrates and agglomerates,
evaporation with hydrofluoric and sulfuric acids.
including sinter products.
Fusion with sodium carbonate and dissolution of the
cooled melt in the filtrate.
Aspiration of the solution obtained into the flame of
an atomic absorption spectrometer using a
dinitrogen oxide-acetylene burner.
2 Normative references
Comparison of the absorbance values obtained for
calcium with those obtained from the calibration
The following standards contain provisions which,
solutions.
through reference in this text, constitute provisions
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All stan-
4 Reagents
dards are subject to revision, and parties to
agreements based on this International Standard
During the analysis, use only reagents of recognized
are encouraged to investigate the possibility of ap-
analytical grade and only distilled water or water of
plying the most recent editions of the standards in-
equivalent purity.
dicated below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
4.1 Sodium carbonate (Na,CO,), anhydrous.
IS0 648:1977, Laboratory glassware - One-mark
4.2 Hydrochloric acid, p I,19 g/ml.
pipettes.
IS0 1042:1983, Laboratory glassware - One-mark
4.3 Hydrochloric acid, p I,19 g/ml, diluted 1 + 9.
volumetric flasks.
4.4 Nitric acid, p I,4 g/ml.
IS0 3081:1986, Iron ores - lncremenf sampling -
Manual method.
4.5 Hydrofluoric acid, p I,13 g/ml, 40 % (m/m), or
p 1,185 g/ml, 48 O/o (m/m).
IS0 3082:1987, Iron ores - Increment sampling and
sample preparation - Mechanical method.
4.6 Sulfuric acid, p I,84 g/ml, diluted 1 + 1.
IS0 3083:1986, Iron ores - Preparation of samples
- Manual method.
4.7 Background solution.
IS0 7764:1985, iron ores - Preparation of predried Dissolve IO g of pure iron wire [minimum purity
99,9 % (m/m), of calcium content less than
test samples for chemical analysis.
1
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IS0 10203:1992(E)
0,0002 % (m/m)] in 50 ml of hydrochloric acid (4.2) 5.3 Atomic absorption spectrometer, equipped with
and oxidize by adding nitric acid (4.4) drop by drop. a di nitrogen oxide-acetylene burner.
Evaporate until a syrupy consistency is obtained.
Add 20 ml of hydrochloric acid (4.2) and dilute to WARNING - Follow the manufacturer’s instructions
200 ml with water. Dissolve 17 g of sodium for igniting and extinguishing the dinitrogen oxide-
carbonate (4.1) in water, add carefully to the iron acetylene flame to avoid possible explosion hazards.
solution and heat to remove carbon dioxide. Trans- Wear tinted safety glasses whenever the flame is
fer the cooled solution to a 1 000 ml one-mark burning,
volumetric flask, dilute to volume with water and
mix. The atomic absorption spectrometer used in this
method shall meet the following criteria.
4.8 Lanthanum chloride solution.
a) Minimum sensitivity - the absorbance of the
Dissolve 50 g of lanthanum chloride (LaCl,.xH,O)
most concentrated calcium calibration solution
[of calcium content less than 0,002 % (m/m)] in (see 4.10) shall be at least 0,3.
50 ml of hydrochloric acid (4.2) and 300 ml of hot
water. Cool and dilute to 1 litre.
b) Graph linearity - the slope of the calibration
graph covering the top 20 % of the concentration
range (expressed as a change in absorbance)
4.9 Calcium standard solution, 25 pg CalmI.
shall not be less than 0,7 of the value of the slope
Dissolve 1,248 7 g of dried calcium carbonate
for the bottom 20 % of the concentration range
(CaCO,) [minimum purity 99,9 % (m/m), dried at
determined in the same way.
105 “C for 1 h] in 100 ml of hydrochloric acid
(p I,19 g/ml), diluted 1 + 3. When dissolved, cool,
Minimum stability - the standard deviation of the
C)
transfer to a 1 000 ml one-mark volumetric flask, di-
absorbance of the most concentrated calibration
lute to volume with water and mix. Transfer 10 ml
solution and that of the zero calibration solution,
of this solution to a 200 ml one-mark volumetric
each being calculated from a sufficient number
flask, dilute to volume with water and mix.
of repetitive measurements, shall be less than
I,5 % and 0,5 % respectively of the mean value
of the absorbance of the most concentrated cali-
4.10 Calcium calibration solutions.
bration solution.
transfer 2,0 ml; 5,0 ml; IO,0 ml;
Using pipettes,
NOTES
20,O ml; 40,O ml; and 50,O ml portions of the calcium
standard solution (4.9) to 200 ml volumetric flasks
2 The use of a strip chart recorder and/or digital readout
(see note 1). Add 6 ml of hydrochloric acid (4.2)
device is recommended to evaluate criteria a) b) and c)
60 ml of background solution (4.7) and 40 ml of
and for all subsequent measurements.
lanthanum chloride solution (4.8) to each flask. Pre-
pare a zero calcium calibration solution by trans-
3 Instrument parameters may vary with each instru-
ferring 60 ml of the background solution (4.7) to a ment. The following parameters were successfully used in
several laboratories and they can be used as guidelines.
200 ml volumetric flask, add 6 ml of hydrochloric
Solutions were aspirated into a dinitrogen oxide-acetylene
acid (4.2) and 40 ml of lanthanum chloride solution.
flame of a premix burner.
Dilute all the solutions to volume with water and
mix.
Hollow cathode lamp, mA 15
422,7
Wavelength, nm
NOTE 1 The range of calcium which can be covered
Dinitrogen oxide flow rate, I/min 13,8
may vary from instrument to instrument. Attention should
Acetylene flow rate, I/min
676
be paid to the minimum criteria given in 5.3. For instru-
In systems where the values shown above for gas flow
ments having high sensitivity, smaller portions of stan-
rates do not apply, the ratio of the gas flow rates may still
dard solution or a more diluted standard solution can be
be a useful guideline.
used.
5 Apparatus
6 Sampling and samples
Ordinary laboratory apparatus, including one-mark
pipettes and one-mark volumetric flasks complying
with the specifications of IS0 648 and IS0 1042 re-
61 . Laboratory sample
spectively, and
For analysis, use a laboratory sample of minus
5.1 Platinum crucible, of minimum capacity 30 ml.
100 pm particle size which has been taken in ac-
cordance with IS0 3081 or IS0 3082 and prepared in
accordance with IS0 3082 or IS0 3083. In the case
5.2 Muffle furnace, capable of maintaining a tem-
of ores having significant contents of combined wa-
perature of approximately 1 100 “C.
2
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IS0 10203:1992(E)
When the analysis is carried out on several samples
ter or oxidizable compounds, use a particle size of
minus 160 pm. of the same type of ore at the same time, the ana-
lytical value of one certified reference material may
NOTE 4 A guideline on significant contents of combined
be used.
water and oxidizable compounds is incorporated in
IS0 7764.
7.4 Determination
6.2 Preparation of predried test samples
7.4.1 Decomposition of the test portion
Thoroughly mix the laboratory sample and, taking
Transfer the test portion (7.2) to a 250 ml beaker.
multiple increments, extract a test sample in such a
Moisten with a few millilitres of water, add 25 ml of
way that it is representative of the whole contents
hydrochloric acid (4.2), cover with a watch-glass and
of the container. Dry the test sample at
heat gently. Increase the heat and digest just below
105 “C + 2 “C, as specified in IS0 7764. (This is the
boiling, until no further attack is apparent. Add 2 ml
predried test sample.)
of nitric acid (4.4) and digest for several minutes.
Remove the watch-glass and evaporate the solution
to dryness. Heat the salts on a hot-plate at 105 “C to
7 Procedure
110 “C for 30 min. Add 5 ml of hydrochloric acid
(4.2) cover the beaker with a watch-glass, and warm
7.1 Number of determinations for several minutes. Add 50 ml of water, stirring to
avoid the hydrolysis of titanium, and heat to boiling.
Carry out the analysis at least in duplicate in ac- Wash the watch-glass and the walls of the beaker
cordance with annex A, independently, on one pre- and filter the solution through a medium-texture pa-
dried test sample. per containing some filter pulp into a 250 ml beaker.
Carefully remove all adhering particles with a
NOTE 5 The expression “independently” means that the
rubber-tipped glass rod or moistened filter paper
second and any subsequent result is not affected by the
and transfer to the filter, washing three times with
previous result(s). For this particular analytical method,
dilute hydrochloric acid (4.3) then with hot water
this condition implies that the repetition of the procedure
until the filter paper is free of iron. Transfer the pa-
is carried out either by the same operator at a different
per and residue to a platinum crucible (5.1). Evap-
time or by a different operator including, in either case,
orate the filtrate to about 100 ml and retain it.
appropriate recalibration.
7.4.2 Treatment of the residue
7.2 Test portion
Ignite the filter paper and residue in a platinum
Taking several increments, weigh, to the nearest
crucible (5.1) at a low temperature (500 OC to
0,000 2 g, approximately 1 g of the predried test
800 “C). Cool, moisten with a few drops of water,
sample obtained in accordance with 6.2.
add 3 or 4 drops of sulfuric acid (4.6) and 10 ml of
hydrofiuoric acid (4.5). Evaporate slowly to expel
NOTE 6 The test portion should be taken and weighed
silica and then fume to remove the excess sulfuric
quickly to avoid reabsorption of moisture.
acid. Ignite at about 700 “C. Add I,0 g of sodium
carbonate (4.1) to the residue (see note 8) cover the
7.3 Blank test and check test
crucible, and fuse over a burner or in a muffle fur-
nace (5.2) until a clear melt is obtained (at about
In each run, one blank test and one analysis of a
1 100 “C for 15 min).
certified reference material of the same type of ore
shall be carried out in parallel with the analysis of NOTE 8 If difficulties are experienced with the fusion,
2 g
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