SIST ISO/TR 11422:2002
(Main)Iron ores -- Recommended procedures for iron ore dissolution using either acid digestion or alkali fusion
Iron ores -- Recommended procedures for iron ore dissolution using either acid digestion or alkali fusion
Recommends procedures for iron ore dissolution using either acid digestion or alkali fusion. Deals with the assessment of the advantages and disadvantages of the two procedures.
Minerais de fer -- Méthodes recommandées de dissolution des minerais de fer par digestion acide ou fusion alcaline
Železove rude - Priporočeni postopki za razkroj železove rude z razklopom v kislini ali raztapljanjem v bazi
General Information
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TECHNICAL
IS0
REPORT
TR 11422
First edition
1996-02-15
Iron ores - Recommended procedures for
iron ore dissolution using either acid
digestion or alkali fusion
Minerais de fer - Mbthodes recommandees de dissolution des minerais
de fer par digestion acide ou fusion alcaline
Reference number
ISOnR 11422: 1996(E)
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ISO/TR 11422: 1996(E)
Contents
Page
1
1 BACKGROUND .
........................................................ 2
SOURCES OF THE RECOMMENDED PROCEDURES
2
3 ASSESSMENT OF ACID DIGESTION VS ALKALI
2
.................................................................................................
FUSION OR SINTER FUSION
.......................................................................................... 3
4 RECOMMENDED PROCEDURES
.................................................................................................... 3
4.1 Acid digestion procedure
...................................................................................................... 9
4.2 Alkali fusion procedure
............................................................................................ 11
4.3 Alkali sinter fusion procedure
A bridged report of international test of three methods
ANNEX A
................................... 14
of ore dissolution in document TC 102/SC2 (DISLN SG-1)
25
Ore dissolution test methods .
ANNEX B
29
............................................
ANNEX C Summary of replies to questionnaire on acid digestion
0 IS0 1996
All rights reserved. Unless otherwise specified, 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 Geneve 20 l Switzerland
Printed in Switzerland
ii
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ISO/TR 11422: 1996(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, governmental 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
electrotechnical standardization.
The main task of technical committees is to prepare International Standards, but in exceptional circumstances
a technical committee may propose the publication of a Technical Report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an International
Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where for any other reason there is
the future but not immediate possibility of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different kind from that which is normally
published as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide
whether they can be transformed into International Standards. Technical Reports of type 3 do not
necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful.
ISO/TR 11422, which is a Technical Report of type 3, was prepared by Technical Committee ISO/TC 102,
Iron ores, Subcommittee SC 2, Chemical analysis.
. . .
111
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TECHNICAL REPORT @ IS0 ISO/TR 11422:1996(E)
Iron ores
- Recommended procedures for iron ore
dissolution using either acid digestion or alkali fusion
1 Background
From time to time in ISO/TC 102/SC 2, the view had been expressed that some degree of
unification of procedures for the dissolution of iron ore test portions, based on selected
established SC 2 procedures, would be of considerable benefit in the development of new
This objective, coupled with the need to investigate possible procedure
analytical methods.
changes when increasing the mass of test portion in trace element methods, led to formation
of the Dissolution Study Group in 1982.
The activities of this Study Group and the details and results of an interlaboratory dissolution
test were reported in document ISO/TC 102/SC 2 N772 E (annexes A and B to this report).
Based on these results and consideration of certain dissolution procedures already in use in
SC 2, several proposed dissolution procedures for various test portion masses were presented
in document ISOJTC 102/SC 2 N887 E, constituting a consolidated study group report for the
period 1982 to 1986.
Before these procedures could be finalized as acceptable models for use in titure analytical
methods, certain discrepancies of detail in the conduct of acid digestions had to be resolved.
Accordingly, SC 2 members’ opinions were invited in the form of an explanatory note and
questionnaire (documents ISO/TC 102/SC 2 N886 E and N888 E). A summary of the replies
is appended (annex C), from which the conclusions to be drawn are as follows:
a) In acid digestions, the beaker should be totally covered; in evaporations it should be
partially covered.
b) Temperatures (obtained in a test beaker) should be, for the initial digestion, 95OC
and, for subsequent digestion and evaporation, 105OC.
c) The evaporation to dehydrate silica should continue to dryness with 15 min further
heating.
d) The fused residue should be leached in the crucible, and not in the reserved main
solution.
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ISOfI’R 11422:1996(E)
0 IS0
These conclusions have been incorporated in the procedures presented in this report It is not
possible to recommend only one method for acid digestion, because of the slightly different
conditions required for varying test portion masses. Accordingly, methods are proposed for
2 g, 1 g and 0,5 g test portions, based on SC 2 methods applicable to or using such test
portions.
An important conclusion from the interlaboratory test was that not all of the parameters
temperature, time of heating and target volume can be specified simultaneously. The test
results showed that, if target volume needs to be specified, temperature and target volume
take precedence, and heating time should be given only as a guide.
2 Sources of the recommended procedures
Acid digestion 4.1.1 2 g test portion IS0 9685: 1991,
tt 4.1.2 1 g test portion IS0 9685: 1991,
M 4.1.3 0.5 g test portion IS0 9682: 1991,
Alkali fusion 4.2.1 IS0 9682: 1991,
tt
.
4.2.1 a SO 4687: 1991,
tt .
.
4.2.2 SO 9683: 1991,
.
Alkali sinter fusion 4.3.1 . SO 1834: 1987,
0 .
4.3.2 I SO 9683: 1991,
NOTE 1 To take into account the survey responses and ot h er considerations, the
recommended procedures differ in minor detail from those in the above sources.
3 Assessment of acid digestion vs alkali fusion or sinter fusion Alkali fusion and sinter
fusion processes have the distinct advantage of providing one-step dissolution which does not
require time-consuming residue treatment; hence they are the first choice wherever possible.
They have the major disadvantage, however, of adding very materially to the salt
concentration of the solution, imposing difficulties with atomic absorption and ICB
measurement techniques. To address this problem, the “8-4-5” low flux ratio procedure
(4.2.1) has been devised to provide the lowest flux-to-sample ratio so far available in iron ore
Where the method can permit a separation of the
dissolution (2,4 flux to 1 test portion).
fusion salts from the analyte, or where spectrophotometric techniques are involved and the
salt concentration is accordingly less relevant, the flux ratio adopted in 4.3.1 (3 flux to 1 test
portion) and in 4.2.2 (4 flux to 1 test portion) can then become acceptable.
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@ IS0 ISO/TR 11422:1996(E)
Alkali fusion or sinter fusion is, in general, limited to test portion masses not greater than
Where trace element determinations requiring 2 g test portions are involved, acid
.
fg
digestion tends to be preferred. However, it would not be impossible to devise an alkali
sinter fusion method with a 2 g test portion and 6 g of sodium peroxide if separation of the
analyte from the high concentration of salts could be contemplated.
4 Recommended procedures
4.1 Acid digestion procedure
4.1.1 2 g test portion
A Reagents
During the procedure, use only water of a grade that complies with IS0 3696:1987, Water for
analytical laboratory use--Specification and test methods.
A.1 Sodium carbonate (Na*CO,), anhydrous.
A.2 Sodium tetraborate (Na2B,O,), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to I,19 g/ml.
A.4 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml, diluted 1 + 1.
A.5 Hydrochloric acid, p 1,16 g/ml to I,19 g/ml, diluted 2 + 100.
A.6 Nitric acid, p 1,4 g/ml.
A.7 Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), or p 1,19 g/ml. 48% (m/m).
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ISO/TR 11422:1996(E)
B Apparatus
Ordinary laboratory equipment, and
B.l Glass beakers, 250 ml capacity.
B.2 Platinum crucibles, minimum capacity 20 ml.
8.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95*C and 105OC.
C Procedure
Transfer a 2,0 g test portion to a 250 ml beaker (13.1) and moisten with water. Add 50 ml of
hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for about 1 h
at a temperature of 95*C.
NOTE 2 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105*C and continue heating, avoiding boiling.
Add 5 ml of nitric acid (A.6) and 0,2 ml of sulfuric acid (A.8), and digest for 15 min at
105*C. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105*C
hotplate setting to dryness. Continue heating for a further 15 min.
NOTE 3 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 30 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 200 ml beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
ter. Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the fil
wash with three or four portions of warm water. Reserve
visibly free from iron, then finally
n solution.
the filtrate and washings as the mai
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
Allow the crucible to cool. Add 0,3 ml of
low temperature, then ignite at 75O*C to 8OOOC.
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 8OO*C for several
4
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0 IS0 ISO/T.R 11422:1996(E)
minutes and cool. Add 0,8 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
and mix. Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
sufficient to produce a clear melt, then allow the crucible to cool.
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.1.2 I g test portion
A Reagents
During the analysis use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium carbonate (Na,CO$ anhydrous.
A2 Sodium tetraborate (Na2B407), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml.
.l to 1,19 g/ml, diluted 1 + 1.
A.4 Hydrochloric acid, p 1,16 g/m
A.5 Hydrochloric acid, p 1,16 g/m ,l to 1,19 g/ml, diluted 2 + 100.
A.6 Nitric acid, Q 1,4 g/ml.
A.7 Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), or p 1,19 g/ml, 48% (m/m).
B Apparatus
Ordinary laboratory equipment, and
B.l Glass beakers, 250 ml capacity.
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ISO/TRll422:1996(E)
8.2 Platinum crucibles, minimum capacity 20 ml.
B3 Hotplate, calibrated using a partial-immersion thermometer,, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95OC and 10S°C.
C Procedure
Transfer a 1,0 g test portion to a 250 ml tall-form beaker (B.l) and moisten with water. Add
25 ml of hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for
about 1 h at a temperature of 95OC.
NOTE 4 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105OC and continue heating, avoiding boiling.
Add 2 ml of nitric acid (A.6) and 0,2 ml of sulfuric acid (A.8), and digest for 15 min at
105OC. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105OC
hotplate setting to dryness. Continue heating for a further 15 min.
NOTE 5 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 2Q0 ml beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the filter.
visibly free from iron, then finally wash with three or four portions of warm water. Reserve
the filtrate and washings as the main solution.
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
low temperature, then ignite at 75OOC to 8OOOC. Allow the crucible to cool. Add 0,3 ml of
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 800°C for several
minutes and cool. Add 0,8 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
and mix.
sufficient to produce a clear melt, then allow the crucible to cool.
l
6
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ISO/TR 11422:1996(E)
@ IS0
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.1,3 0,5 g test portion
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1
Sodium carbonate (Na$Os), anhydrous.
A.2 Sodium tetraborate (Na,B,O,), anhydrous.
A.3 Hydrochloric acid, p I,16 g/ml to 1,19 g/ml.
A.4 Hydrochloric acid, p 1,16 g/m 1 to 1,19 g/ml, diluted 1 + 1.
I to 1,19 g/ml, diluted 2 + 100.
A.5 Hydrochlsric acid, p 1,16 g/m
A.6 Nitric acid, p 1,4 g/ml.
A.7
Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p I,13 g/ml, 40% (m/m), p 1,19 g/ml, 48% (m/m).
B Apparatus
Ordinary laboratory equipment, and
B.1 Glass beakers, 250 ml capacity.
B.2
Platinum crucibles, minimum capacity 20 ml.
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@ IS0
ISO/TR 11422: 1996(E)
B.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95OC and 105%
C Procedure
Transfer a 0,5 g test portion to a 250 ml tall-form beaker (B.l) and moisten with water. Add
20 ml of hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for
abut 1 h at a temperature of 95OC.
NOTE 6 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105OC and continue heating, avoiding boiling.
Add 2 ml of nitric acid (A.6), 02 ml of sulfuric acid (A.8) and digest for 15 min at 105OC.
Displace the cover to provide a 6 mm gap and evaporate the solution at the 105°C hotplate
setting to dryness. Continue heating for a further 15 min.
NOTE 7 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 200 mll beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the filter.
visibly free from iron, then finally wash with three or four portions of warm water. Reserve
the filtrate and washings as the main solution.
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
low temperature, then ignite at 75OOC to 8OOOC. Allow the crucible to cool. Add 0,3 ml of
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 8OOOC for several
minutes and cool. Add 08 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
and mix. Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
sufficient to produce a clear melt, then allow the crucible to cool.
8
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ISO/T.R 11422:1996(E)
@ IS0
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.2 Alkali fusion procedure
4.2.1 Carbonate-borate flux (8-4-S flux)-0,5 g test portion
Na,C03 : 0,8 g
: 0,4 g
Na2B407
Test portion :
03 g
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium carbonate (Na2C03), anhydrous.
A.2 Sodium tettaborate (Na,B,O,), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to 1.19 g/ml, diluted 1 + 1.
B Apparatus
Ordinary laboratory equipment, and
B.1 Platinum or suitable platinum-alloy crucibles, minimum capacity 25 ml.
B.2 Muffle furnace, suitable for operation at a controlled temperature of 102OOC.
B.3 Combined magnetic stirrer-hotplate.
B.4
Stirring bars, polytetrafluoroethylene (PTFE)-coated, 10 mm long.
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ISO/TR 11422:1996(E)
C Procedure
Add 0,80 g of sodium carbonate (A.l) to a platinum crucible (B.l), transfer the 0,s g test
portion to the crucible and mix well using a platinum or stainless steel rod. Add 0,4 g of
sodium tetraborate (A.2) and repeat the mixing using the metal rod. Place the crucible in a
muffle furnace (B.2) at 1020°C, for 30 min. Remove the crucible and quickly roll the melt as
it solidifies. Allow to cool, then place a PTFE-coated stirring bar (B.4) in the cnncible and
place the crucible on its side in a 150 ml low-form beaker. Add 30 ml of hydrochloric acid
(A.3) and 30 ml of water, cover and heat with stirring on a magnetic stirrer - hotplate (B.3)
until dissolution of the melt is complete.
NOTE 8 The crucible may need to be rolled to ensure complete dissolution of the
melt.
Remove and rinse the crucible and stirrer, cool the solution and transfer to a 100 ml
volumetric flask. Dilute to volume with water and mix. (This is the test solution.)
4.2.2 Sodium peroxide-O,5 g test portion
.
.
2g
Test portion : 03 g
NOTE 9 Direct fusions over a burner can produce mechanical Posses with certain reactive
ores. In this case, a preliminary sinter (4.3.2) may be indicated.
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium peroxide (Na202), dry, fine powder.
A.2 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml, diluted l+ 1.
B Apparatus
Ordinary laboratory equipment, and
B.l Vitreous carbon crucible, or zirconium metal crucible, 50 ml capacity.
10
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ISO/TR 11422:1996(E)
0 IS0
C Procedure
Transfer 2,0 g of sodium peroxide (A.1) to a dry crucible (B.l). Add the 0,s g of test portion
and mix well with a dry spatula. Fuse over a Meker burner (low heat), swirling the crucible
until the melt is cherry-red and clear.
Remove from the heat, swirl until the melt solidifies
on the inner wall of the crucible, place the crucible upright in a dry 300 ml beaker, and cover
the beaker with a watch glass.
When cool, add about 5 ml of water into the crucible. After effervescence ceases, heat to
complete decomposition, empty the contents of the crucible into the beaker and wash the
crucible with about 10 ml of water. Add 20 ml of hydrochloric acid (A.2) via the crucible
into the beaker. Rinse the crucible with water and acid as appropriate, and add the rinsings to
the beaker. Boil to dissolve any residual material, cool, and dilute to specified volume as
required. (This is the test solution.)
4.3 Alkali sinter fusion procedure
4.3.1 Sodium peroxide-l g test portion
Na202 : 3 g
Test portion : 1 g
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium peroxide (Na,O,), dry, fine powder.
A.2 Hydrochloric acid, p lJ6 g/ml to I,19 g/ml.
B Apparatus
Ordinary laboratory equipment, and
B.l Zirconium or vitreous carbon crucibles, approximately 30 ml capacity.
11
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ISO/TR 11422:1996(E)
8.2 Muffle furnace, to provide a cootrolled temperature at 52OOC.
C Procedure
Weigh into a zirconium or vitreous carbon crucible (B.1) 3 g of sodium peroxide (A.1) and
Mix with a thin non-magnetic metal spatula or
immediately add the weighed 1 g test portion.
glass rod and place in a muffle furnace (B.2) at 520°C flO”C for 15 min. Remove from the
furnace and heat on a Meker burner to the melting point with swirling, and continue the
heating with swirling for 1 min to 2 min, to dissolve residual particles. Cool to room
temperature (the crucible may be placed on a metal block if desired), add 20 ml of water, and
cover. Heat on a hotplate just to boiling point, to complete the disintegration, and transfer
the crucible contents to a 200 ml or 250 ml t&cer with rinsing. Add 5 ml of water and
20 ml of hydrochloric acid (A.2) to the crucible, and warm to dissolve any residual material.
Transfer the solution to the beaker with rinsing, cover and boil gently to expel chlorine. Cool
and dilute to specified volume, as required. (This is the test solution.)
4.3.2 Sodium peroxide-O,5 g test pwtion
Na202 : 2 g
Test portion : 0,5 g
A Reagents
A.1 Sodium peroxide, (Na,O,), dry, fine powder
A.2 Hydrochloric acid, p 1,16 g/m1 to 1,19 g/m
B Apparatus
Ordinary laboratory equipment, and
B.l Zirconium or vitreous carbon crucibles, approximately 30 ml capacity.
B.2 Muffle furnace, to provide a controlled temperature at 52OOC.
12
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ISO/TR 11422:1996(E)
@ IS0
C Procedure
Weigh into a zirconium or vitreous carbon crucible (B.l) 2 g of sodium peroxide (A.l) and
immediately add the weighed 0,5 g test portion. Mix with a thin metal spatula or glass rod
and place in a muffle furnace (B.2) at 52OOC *lO°C for 15 min. Remove from the furnace
and heat on a Meker burner to the melting point with swirling, and continue the heating with
swirling for 1 min to 2 min to dissolve residual particles. Cool to room temperature (the
crucible may be placed on a metal block if desired), add 20 ml of water and cover. Heat on a
hotplate just to boiling point to complete the disintegration, and transfer the crucible contents
to a 200 ml or 250 ml beaker with rinsing. Add 5 ml of water and 15 ml of hydrochloric
acid (A.2) to the crucible, and warm to dissolve any residual material. Transfer the solution
to the beaker with rinsing, cover and boil gently to expel chlorine. Cool and dilute to
specified volume, as required. (This is the test solution.)
13
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ISO/TR 11422:1996(E)
Annex A
Abridged report of international test of three methods of ore
dissolution in document TC 102&C 2 (DISLN SG-1)
A.1 Background of the test programme
Previous discussions at TC 102/SC 2 meetings (Pretoria 1980, Ottawa 1982), leading to
Resolutions 43 and 4 respectively at those meetings, have centred essentially on the one
major question of whether an increase in the mass of test portion to 2 g for trace element
determinations should require any technical change in the acid-attack methods of iron ore
dissolution used in the past. These established methods involve: digestion with hydrochloric
acid; evaporation to dehydrate silica (either by evaporation to dryness or with perchloric
acid); dissolution of salts; and filtration and ignition of the silica. After removal of silica
with hydrofluoric acid, any residue is fused with either an acid or an alkaline flux, dissolved
and combined with the main solution. The several variants based on this general principle are
typified in such existing ISO/TC 102 Standards as:
Perchloric dehydration Hydrochloric dehydration
IS0 4692 Ca/Mg
IS0 2599 P
IS0 3886 Mn
IS0 4687 P
IS0 4693 Cu
IS0 5418 Cu
The major problem that could arise with an increase of test portion to 2 g is that with high
silica contents the filtration and washing of up to 600 mg of SiO, could be a difficult and
inconvenient operation if the silica were present in a gelatinous form. In many cases, of
course, the silica would be present as quartz, with filtration and washing problems being
greatly diminished. An alternative technique to avoid problems from high amounts of
gelatinous silica is to remove the silica during the ore-dissolution process with hydrofluoric
acid, using a PTFE beaker. This technique has been used already in IS0 6831 Na/K,
although for the different reason of avoiding contamination.
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@ IS0 ISO/TR 11422:1996(E)
A.2 Aim of the test programme
The aim of the present test programme was to examine three methods of ore dissolution
derived from the alternatives discussed above (but without using perchloric acid) as follows:
Method 1
The established procedure using hydrochloric acid dehydration of silica and silica filtration,
improved to accommodate a 2 g test portion by using a larger beaker and specified
temperatures for digestion and evaporation.
Method 2
Digestion in a PTFE beaker with hydrochloric and hydrofluoric acids to eliminate silica
before filtration of any unattacked residue.
Method 3
Same as method 2, but witi preliminary digestion with hydrochloric acid in glass before
transfer to PTFE and addition of hydrofluoric acid.
Features of the test programme
The comparison of the three methods was made on the basis of:
1 Determining the time taken to prepare the stock solution (excluding drying and ignition
of filter papers, because this could be either a slow or a fast operation depending on
individual laboratory skills or preferences).
2 Determining the nta~~ of any acid-insoluble residue (excluding silica, this having been
volatilized with hydrofluoric acid either before filtration (Methods 2 and 3), or in the
platinum crucible (Method 1). Mass of residue influences the amount of flux required.
The amount of flux may be either important or not important, depending on subsequent
operations in the method.
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ISO/TR 11422:1996(E) 0 IS0
3 The volume of filtrate could be of interest in the overall aim of obtaining a 100 ml final
volume of stock solution.
Test samples
The following samples were chosen for various reasons to highlight particular features that
could cause problems in one or other of the three methods:
Reason for choice
Test Sample
High Ca
79-4 Lorraine
83-l 1 Hamersley High Si
Medium Si
83-12 Mt Newman
Koolan HG High grade
83-13
83-14 Solmer High Ti
Analytical data on these samples are available in Document 2N 744E.
Details of the three methods tested, and the test results, are given in tables A,1 to AS.
Results for each sample indicate the average time taken and the average mass of residue. The
averages for all samples are collated in a summary and given in table A.6. The grand means
for all samples are given in table A.7.
16
---------------------- Page: 20 --------------
...
SLOVENSKI STANDARD
SIST ISO/TR 11422:2002
01-januar-2002
äHOH]RYHUXGH3ULSRURþHQLSRVWRSNL]DUD]NURMåHOH]RYHUXGH]UD]NORSRPYNLVOLQL
DOLUD]WDSOMDQMHPYED]L
Iron ores -- Recommended procedures for iron ore dissolution using either acid digestion
or alkali fusion
Minerais de fer -- Méthodes recommandées de dissolution des minerais de fer par
digestion acide ou fusion alcaline
Ta slovenski standard je istoveten z: ISO/TR 11422:1996
ICS:
73.060.10 Železove rude Iron ores
SIST ISO/TR 11422:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO/TR 11422:2002
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SIST ISO/TR 11422:2002
TECHNICAL
IS0
REPORT
TR 11422
First edition
1996-02-15
Iron ores - Recommended procedures for
iron ore dissolution using either acid
digestion or alkali fusion
Minerais de fer - Mbthodes recommandees de dissolution des minerais
de fer par digestion acide ou fusion alcaline
Reference number
ISOnR 11422: 1996(E)
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SIST ISO/TR 11422:2002
ISO/TR 11422: 1996(E)
Contents
Page
1
1 BACKGROUND .
........................................................ 2
SOURCES OF THE RECOMMENDED PROCEDURES
2
3 ASSESSMENT OF ACID DIGESTION VS ALKALI
2
.................................................................................................
FUSION OR SINTER FUSION
.......................................................................................... 3
4 RECOMMENDED PROCEDURES
.................................................................................................... 3
4.1 Acid digestion procedure
...................................................................................................... 9
4.2 Alkali fusion procedure
............................................................................................ 11
4.3 Alkali sinter fusion procedure
A bridged report of international test of three methods
ANNEX A
................................... 14
of ore dissolution in document TC 102/SC2 (DISLN SG-1)
25
Ore dissolution test methods .
ANNEX B
29
............................................
ANNEX C Summary of replies to questionnaire on acid digestion
0 IS0 1996
All rights reserved. Unless otherwise specified, 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 Geneve 20 l Switzerland
Printed in Switzerland
ii
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SIST ISO/TR 11422:2002
ISO/TR 11422: 1996(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, governmental 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
electrotechnical standardization.
The main task of technical committees is to prepare International Standards, but in exceptional circumstances
a technical committee may propose the publication of a Technical Report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an International
Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where for any other reason there is
the future but not immediate possibility of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different kind from that which is normally
published as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide
whether they can be transformed into International Standards. Technical Reports of type 3 do not
necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful.
ISO/TR 11422, which is a Technical Report of type 3, was prepared by Technical Committee ISO/TC 102,
Iron ores, Subcommittee SC 2, Chemical analysis.
. . .
111
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SIST ISO/TR 11422:2002
TECHNICAL REPORT @ IS0 ISO/TR 11422:1996(E)
Iron ores
- Recommended procedures for iron ore
dissolution using either acid digestion or alkali fusion
1 Background
From time to time in ISO/TC 102/SC 2, the view had been expressed that some degree of
unification of procedures for the dissolution of iron ore test portions, based on selected
established SC 2 procedures, would be of considerable benefit in the development of new
This objective, coupled with the need to investigate possible procedure
analytical methods.
changes when increasing the mass of test portion in trace element methods, led to formation
of the Dissolution Study Group in 1982.
The activities of this Study Group and the details and results of an interlaboratory dissolution
test were reported in document ISO/TC 102/SC 2 N772 E (annexes A and B to this report).
Based on these results and consideration of certain dissolution procedures already in use in
SC 2, several proposed dissolution procedures for various test portion masses were presented
in document ISOJTC 102/SC 2 N887 E, constituting a consolidated study group report for the
period 1982 to 1986.
Before these procedures could be finalized as acceptable models for use in titure analytical
methods, certain discrepancies of detail in the conduct of acid digestions had to be resolved.
Accordingly, SC 2 members’ opinions were invited in the form of an explanatory note and
questionnaire (documents ISO/TC 102/SC 2 N886 E and N888 E). A summary of the replies
is appended (annex C), from which the conclusions to be drawn are as follows:
a) In acid digestions, the beaker should be totally covered; in evaporations it should be
partially covered.
b) Temperatures (obtained in a test beaker) should be, for the initial digestion, 95OC
and, for subsequent digestion and evaporation, 105OC.
c) The evaporation to dehydrate silica should continue to dryness with 15 min further
heating.
d) The fused residue should be leached in the crucible, and not in the reserved main
solution.
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SIST ISO/TR 11422:2002
ISOfI’R 11422:1996(E)
0 IS0
These conclusions have been incorporated in the procedures presented in this report It is not
possible to recommend only one method for acid digestion, because of the slightly different
conditions required for varying test portion masses. Accordingly, methods are proposed for
2 g, 1 g and 0,5 g test portions, based on SC 2 methods applicable to or using such test
portions.
An important conclusion from the interlaboratory test was that not all of the parameters
temperature, time of heating and target volume can be specified simultaneously. The test
results showed that, if target volume needs to be specified, temperature and target volume
take precedence, and heating time should be given only as a guide.
2 Sources of the recommended procedures
Acid digestion 4.1.1 2 g test portion IS0 9685: 1991,
tt 4.1.2 1 g test portion IS0 9685: 1991,
M 4.1.3 0.5 g test portion IS0 9682: 1991,
Alkali fusion 4.2.1 IS0 9682: 1991,
tt
.
4.2.1 a SO 4687: 1991,
tt .
.
4.2.2 SO 9683: 1991,
.
Alkali sinter fusion 4.3.1 . SO 1834: 1987,
0 .
4.3.2 I SO 9683: 1991,
NOTE 1 To take into account the survey responses and ot h er considerations, the
recommended procedures differ in minor detail from those in the above sources.
3 Assessment of acid digestion vs alkali fusion or sinter fusion Alkali fusion and sinter
fusion processes have the distinct advantage of providing one-step dissolution which does not
require time-consuming residue treatment; hence they are the first choice wherever possible.
They have the major disadvantage, however, of adding very materially to the salt
concentration of the solution, imposing difficulties with atomic absorption and ICB
measurement techniques. To address this problem, the “8-4-5” low flux ratio procedure
(4.2.1) has been devised to provide the lowest flux-to-sample ratio so far available in iron ore
Where the method can permit a separation of the
dissolution (2,4 flux to 1 test portion).
fusion salts from the analyte, or where spectrophotometric techniques are involved and the
salt concentration is accordingly less relevant, the flux ratio adopted in 4.3.1 (3 flux to 1 test
portion) and in 4.2.2 (4 flux to 1 test portion) can then become acceptable.
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SIST ISO/TR 11422:2002
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Alkali fusion or sinter fusion is, in general, limited to test portion masses not greater than
Where trace element determinations requiring 2 g test portions are involved, acid
.
fg
digestion tends to be preferred. However, it would not be impossible to devise an alkali
sinter fusion method with a 2 g test portion and 6 g of sodium peroxide if separation of the
analyte from the high concentration of salts could be contemplated.
4 Recommended procedures
4.1 Acid digestion procedure
4.1.1 2 g test portion
A Reagents
During the procedure, use only water of a grade that complies with IS0 3696:1987, Water for
analytical laboratory use--Specification and test methods.
A.1 Sodium carbonate (Na*CO,), anhydrous.
A.2 Sodium tetraborate (Na2B,O,), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to I,19 g/ml.
A.4 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml, diluted 1 + 1.
A.5 Hydrochloric acid, p 1,16 g/ml to I,19 g/ml, diluted 2 + 100.
A.6 Nitric acid, p 1,4 g/ml.
A.7 Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), or p 1,19 g/ml. 48% (m/m).
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SIST ISO/TR 11422:2002
ISO/TR 11422:1996(E)
B Apparatus
Ordinary laboratory equipment, and
B.l Glass beakers, 250 ml capacity.
B.2 Platinum crucibles, minimum capacity 20 ml.
8.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95*C and 105OC.
C Procedure
Transfer a 2,0 g test portion to a 250 ml beaker (13.1) and moisten with water. Add 50 ml of
hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for about 1 h
at a temperature of 95*C.
NOTE 2 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105*C and continue heating, avoiding boiling.
Add 5 ml of nitric acid (A.6) and 0,2 ml of sulfuric acid (A.8), and digest for 15 min at
105*C. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105*C
hotplate setting to dryness. Continue heating for a further 15 min.
NOTE 3 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 30 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 200 ml beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
ter. Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the fil
wash with three or four portions of warm water. Reserve
visibly free from iron, then finally
n solution.
the filtrate and washings as the mai
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
Allow the crucible to cool. Add 0,3 ml of
low temperature, then ignite at 75O*C to 8OOOC.
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 8OO*C for several
4
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SIST ISO/TR 11422:2002
0 IS0 ISO/T.R 11422:1996(E)
minutes and cool. Add 0,8 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
and mix. Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
sufficient to produce a clear melt, then allow the crucible to cool.
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.1.2 I g test portion
A Reagents
During the analysis use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium carbonate (Na,CO$ anhydrous.
A2 Sodium tetraborate (Na2B407), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml.
.l to 1,19 g/ml, diluted 1 + 1.
A.4 Hydrochloric acid, p 1,16 g/m
A.5 Hydrochloric acid, p 1,16 g/m ,l to 1,19 g/ml, diluted 2 + 100.
A.6 Nitric acid, Q 1,4 g/ml.
A.7 Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), or p 1,19 g/ml, 48% (m/m).
B Apparatus
Ordinary laboratory equipment, and
B.l Glass beakers, 250 ml capacity.
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SIST ISO/TR 11422:2002
ISO/TRll422:1996(E)
8.2 Platinum crucibles, minimum capacity 20 ml.
B3 Hotplate, calibrated using a partial-immersion thermometer,, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95OC and 10S°C.
C Procedure
Transfer a 1,0 g test portion to a 250 ml tall-form beaker (B.l) and moisten with water. Add
25 ml of hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for
about 1 h at a temperature of 95OC.
NOTE 4 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105OC and continue heating, avoiding boiling.
Add 2 ml of nitric acid (A.6) and 0,2 ml of sulfuric acid (A.8), and digest for 15 min at
105OC. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105OC
hotplate setting to dryness. Continue heating for a further 15 min.
NOTE 5 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 2Q0 ml beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the filter.
visibly free from iron, then finally wash with three or four portions of warm water. Reserve
the filtrate and washings as the main solution.
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
low temperature, then ignite at 75OOC to 8OOOC. Allow the crucible to cool. Add 0,3 ml of
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 800°C for several
minutes and cool. Add 0,8 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
and mix.
sufficient to produce a clear melt, then allow the crucible to cool.
l
6
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@ IS0
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.1,3 0,5 g test portion
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1
Sodium carbonate (Na$Os), anhydrous.
A.2 Sodium tetraborate (Na,B,O,), anhydrous.
A.3 Hydrochloric acid, p I,16 g/ml to 1,19 g/ml.
A.4 Hydrochloric acid, p 1,16 g/m 1 to 1,19 g/ml, diluted 1 + 1.
I to 1,19 g/ml, diluted 2 + 100.
A.5 Hydrochlsric acid, p 1,16 g/m
A.6 Nitric acid, p 1,4 g/ml.
A.7
Sulfuric acid, p 1,84 g/ml.
A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1.
A.9 Hydrofluoric acid, p I,13 g/ml, 40% (m/m), p 1,19 g/ml, 48% (m/m).
B Apparatus
Ordinary laboratory equipment, and
B.1 Glass beakers, 250 ml capacity.
B.2
Platinum crucibles, minimum capacity 20 ml.
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SIST ISO/TR 11422:2002
@ IS0
ISO/TR 11422: 1996(E)
B.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm
depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95OC and 105%
C Procedure
Transfer a 0,5 g test portion to a 250 ml tall-form beaker (B.l) and moisten with water. Add
20 ml of hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for
abut 1 h at a temperature of 95OC.
NOTE 6 If after this digestion the amount of insoluble residue is high, raise the
hotplate temperature to about 105OC and continue heating, avoiding boiling.
Add 2 ml of nitric acid (A.6), 02 ml of sulfuric acid (A.8) and digest for 15 min at 105OC.
Displace the cover to provide a 6 mm gap and evaporate the solution at the 105°C hotplate
setting to dryness. Continue heating for a further 15 min.
NOTE 7 If the test sample contains significant amounts of barium, omit the addition of
sulfuric acid.
Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and
mix, then wash the watch glass and wall of the beaker and filter the solution through a
close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 200 mll beaker.
Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened
Wash the paper with hydrochloric acid (A.5) until
filter paper and transfer to the filter.
visibly free from iron, then finally wash with three or four portions of warm water. Reserve
the filtrate and washings as the main solution.
Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a
low temperature, then ignite at 75OOC to 8OOOC. Allow the crucible to cool. Add 0,3 ml of
sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon
dioxide, then continue heating to remove the sulfuric acid. Ignite at 8OOOC for several
minutes and cool. Add 08 g of sodium carbonate (A.l) and 0,4 g of sodium tetraborate (A.2)
and mix. Heat at 1000°C in a muffle furnace or over a pressurized air burner for a period
sufficient to produce a clear melt, then allow the crucible to cool.
8
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SIST ISO/TR 11422:2002
ISO/T.R 11422:1996(E)
@ IS0
Add 10 ml of hydrochloric acid (A.4) and heat to dissolve the melt and expel carbon dioxide.
Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml
volumetric flask, dilute to volume and mix. (This is the test solution.)
4.2 Alkali fusion procedure
4.2.1 Carbonate-borate flux (8-4-S flux)-0,5 g test portion
Na,C03 : 0,8 g
: 0,4 g
Na2B407
Test portion :
03 g
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium carbonate (Na2C03), anhydrous.
A.2 Sodium tettaborate (Na,B,O,), anhydrous.
A.3 Hydrochloric acid, p 1,16 g/ml to 1.19 g/ml, diluted 1 + 1.
B Apparatus
Ordinary laboratory equipment, and
B.1 Platinum or suitable platinum-alloy crucibles, minimum capacity 25 ml.
B.2 Muffle furnace, suitable for operation at a controlled temperature of 102OOC.
B.3 Combined magnetic stirrer-hotplate.
B.4
Stirring bars, polytetrafluoroethylene (PTFE)-coated, 10 mm long.
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SIST ISO/TR 11422:2002
ISO/TR 11422:1996(E)
C Procedure
Add 0,80 g of sodium carbonate (A.l) to a platinum crucible (B.l), transfer the 0,s g test
portion to the crucible and mix well using a platinum or stainless steel rod. Add 0,4 g of
sodium tetraborate (A.2) and repeat the mixing using the metal rod. Place the crucible in a
muffle furnace (B.2) at 1020°C, for 30 min. Remove the crucible and quickly roll the melt as
it solidifies. Allow to cool, then place a PTFE-coated stirring bar (B.4) in the cnncible and
place the crucible on its side in a 150 ml low-form beaker. Add 30 ml of hydrochloric acid
(A.3) and 30 ml of water, cover and heat with stirring on a magnetic stirrer - hotplate (B.3)
until dissolution of the melt is complete.
NOTE 8 The crucible may need to be rolled to ensure complete dissolution of the
melt.
Remove and rinse the crucible and stirrer, cool the solution and transfer to a 100 ml
volumetric flask. Dilute to volume with water and mix. (This is the test solution.)
4.2.2 Sodium peroxide-O,5 g test portion
.
.
2g
Test portion : 03 g
NOTE 9 Direct fusions over a burner can produce mechanical Posses with certain reactive
ores. In this case, a preliminary sinter (4.3.2) may be indicated.
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium peroxide (Na202), dry, fine powder.
A.2 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml, diluted l+ 1.
B Apparatus
Ordinary laboratory equipment, and
B.l Vitreous carbon crucible, or zirconium metal crucible, 50 ml capacity.
10
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ISO/TR 11422:1996(E)
0 IS0
C Procedure
Transfer 2,0 g of sodium peroxide (A.1) to a dry crucible (B.l). Add the 0,s g of test portion
and mix well with a dry spatula. Fuse over a Meker burner (low heat), swirling the crucible
until the melt is cherry-red and clear.
Remove from the heat, swirl until the melt solidifies
on the inner wall of the crucible, place the crucible upright in a dry 300 ml beaker, and cover
the beaker with a watch glass.
When cool, add about 5 ml of water into the crucible. After effervescence ceases, heat to
complete decomposition, empty the contents of the crucible into the beaker and wash the
crucible with about 10 ml of water. Add 20 ml of hydrochloric acid (A.2) via the crucible
into the beaker. Rinse the crucible with water and acid as appropriate, and add the rinsings to
the beaker. Boil to dissolve any residual material, cool, and dilute to specified volume as
required. (This is the test solution.)
4.3 Alkali sinter fusion procedure
4.3.1 Sodium peroxide-l g test portion
Na202 : 3 g
Test portion : 1 g
A Reagents
During the analysis, use only water of a grade that complies with IS0 3696:1987.
A.1 Sodium peroxide (Na,O,), dry, fine powder.
A.2 Hydrochloric acid, p lJ6 g/ml to I,19 g/ml.
B Apparatus
Ordinary laboratory equipment, and
B.l Zirconium or vitreous carbon crucibles, approximately 30 ml capacity.
11
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ISO/TR 11422:1996(E)
8.2 Muffle furnace, to provide a cootrolled temperature at 52OOC.
C Procedure
Weigh into a zirconium or vitreous carbon crucible (B.1) 3 g of sodium peroxide (A.1) and
Mix with a thin non-magnetic metal spatula or
immediately add the weighed 1 g test portion.
glass rod and place in a muffle furnace (B.2) at 520°C flO”C for 15 min. Remove from the
furnace and heat on a Meker burner to the melting point with swirling, and continue the
heating with swirling for 1 min to 2 min, to dissolve residual particles. Cool to room
temperature (the crucible may be placed on a metal block if desired), add 20 ml of water, and
cover. Heat on a hotplate just to boiling point, to complete the disintegration, and transfer
the crucible contents to a 200 ml or 250 ml t&cer with rinsing. Add 5 ml of water and
20 ml of hydrochloric acid (A.2) to the crucible, and warm to dissolve any residual material.
Transfer the solution to the beaker with rinsing, cover and boil gently to expel chlorine. Cool
and dilute to specified volume, as required. (This is the test solution.)
4.3.2 Sodium peroxide-O,5 g test pwtion
Na202 : 2 g
Test portion : 0,5 g
A Reagents
A.1 Sodium peroxide, (Na,O,), dry, fine powder
A.2 Hydrochloric acid, p 1,16 g/m1 to 1,19 g/m
B Apparatus
Ordinary laboratory equipment, and
B.l Zirconium or vitreous carbon crucibles, approximately 30 ml capacity.
B.2 Muffle furnace, to provide a controlled temperature at 52OOC.
12
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@ IS0
C Procedure
Weigh into a zirconium or vitreous carbon crucible (B.l) 2 g of sodium peroxide (A.l) and
immediately add the weighed 0,5 g test portion. Mix with a thin metal spatula or glass rod
and place in a muffle furnace (B.2) at 52OOC *lO°C for 15 min. Remove from the furnace
and heat on a Meker burner to the melting point with swirling, and continue the heating with
swirling for 1 min to 2 min to dissolve residual particles. Cool to room temperature (the
crucible may be placed on a metal block if desired), add 20 ml of water and cover. Heat on a
hotplate just to boiling point to complete the disintegration, and transfer the crucible contents
to a 200 ml or 250 ml beaker with rinsing. Add 5 ml of water and 15 ml of hydrochloric
acid (A.2) to the crucible, and warm to dissolve any residual material. Transfer the solution
to the beaker with rinsing, cover and boil gently to expel chlorine. Cool and dilute to
specified volume, as required. (This is the test solution.)
13
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ISO/TR 11422:1996(E)
Annex A
Abridged report of international test of three methods of ore
dissolution in document TC 102&C 2 (DISLN SG-1)
A.1 Background of the test programme
Previous discussions at TC 102/SC 2 meetings (Pretoria 1980, Ottawa 1982), leading to
Resolutions 43 and 4 respectively at those meetings, have centred essentially on the one
major question of whether an increase in the mass of test portion to 2 g for trace element
determinations should require any technical change in the acid-attack methods of iron ore
dissolution used in the past. These established methods involve: digestion with hydrochloric
acid; evaporation to dehydrate silica (either by evaporation to dryness or with perchloric
acid); dissolution of salts; and filtration and ignition of the silica. After removal of silica
with hydrofluoric acid, any residue is fused with either an acid or an alkaline flux, dissolved
and combined with the main solution. The several variants based on this general principle are
typified in such existing ISO/TC 102 Standards as:
Perchloric dehydration Hydrochloric dehydration
IS0 4692 Ca/Mg
IS0 2599 P
IS0 3886 Mn
IS0 4687 P
IS0 4693 Cu
IS0 5418 Cu
The major problem that could arise with an increase of test portion to 2 g is that with high
silica contents the filtration and washing of up to 600 mg of SiO, could be a difficult and
inconvenient operation if the silica were present in a gelatinous form. In many cases, of
course, the silica would be present as quartz, with filtration and washing problems being
greatly diminished. An alternative technique to avoid problems from high amounts of
gelatinous silica is to remove the silica during the ore-dissolution process with hydrofluoric
acid, using a PTFE beaker. This technique has been used already in IS0 6831 Na/K,
although for the different reason of avoiding contamination.
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SIST ISO/TR 11422:2002
@ IS0 ISO/TR 11422:1996(E)
A.2 Aim of the test programme
The aim of the present test programme was to examine three methods of ore dissolution
derived from the alternatives discussed above (but without using perchloric acid) as follows:
Method 1
The established procedure using hydrochloric acid dehydration of silica and silica filtration,
improved to accommodate a 2 g test portion by using a larger beaker and specified
temperatures for digestion and evaporation.
Method 2
Digestion in a PTFE beaker with hydrochloric and hydrofluoric acids to eliminate silica
before filtration of any unattacked residue.
Method 3
Same as method 2, but witi preliminary digestion with hydrochloric acid in glass before
transfer to PTFE and addition of hydrofluoric acid.
Features of the test programme
The comparison of the three methods was made on the basis of:
1 Determining the time taken to prepare the stock solution (excluding drying and ignition
of filter papers, because this could be either a slow or a fast operation depending on
individual laboratory skills or preferences).
2 Determining the nta~~ of any acid-insoluble residue (excluding silica, this having been
volatilized with hydrofluoric ac
...
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