ISO 15249:1998

SLOVENSKI STANDARD
SIST ISO 15249:2000
01-junij-2000
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Zinc sulfide concentrates -- Determination of gold content -- Acid dissolution/solvent
extraction/flame atomic absorption spectrometric method
Concentrés sulfurés de zinc -- Dosage de l'or -- Méthode par dissolution acide, extraction
à l'aide d'un solvant et spectrométrie d'absorption atomique dans la flamme
Ta slovenski standard je istoveten z: ISO 15249:1998
ICS:
73.060.99 Druge rude Other metalliferous minerals
SIST ISO 15249:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 15249:2000

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SIST ISO 15249:2000
INTERNATIONAL ISO
STANDARD 15249
First edition
1998-12-15
Zinc sulfide concentrates — Determination
of gold content — Acid dissolution/solvent
extraction/flame atomic absorption
spectrometric method
Concentrés sulfurés de zinc — Dosage de l’or — Méthode par dissolution
acide, extraction à l’aide d’un solvant et spectrométrie d’absorption
atomique dans la flamme
A
Reference number
ISO 15249:1998(E)

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SIST ISO 15249:2000
ISO 15249:1998(E)
Contents Page
1 Scope .1
2 Normative references .1
3 Principle.1
4 Reagents.1
5 Apparatus .3
6 Sample .3
7 Procedure .3
8 Expression of results .5
9 Precision.5
10 Test report .7
Annex A (normative) Procedure for the preparation and determination of the mass of a predried
test portion .8
Annex B (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples .10
Annex C (informative) Derivation of precision equations .11
Annex D (informative) Bibliography .16
©  ISO 1998
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 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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SIST ISO 15249:2000
© ISO
ISO 15249:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO 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. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard ISO 15249 was prepared by Technical Commitee ISO/TC 183, Copper, lead and zinc ores.
Annexes A and B form an integral part of this International Standard. Annexes C and D are for information only.
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SIST ISO 15249:2000

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SIST ISO 15249:2000
INTERNATIONAL STANDARD  © ISO ISO 15249:1998(E)
Zinc sulfide concentrates — Determination of gold content —
Acid dissolution/solvent extraction/flame atomic absorption
spectrometric method
1 Scope
This International Standard specifies an acid decomposition, solvent extraction, flame atomic absorption spectrometric
procedure for the determination of gold in zinc sulfide concentrates.
The method is applicable to the determination of gold in zinc concentrates containing up to 60 % (m/m) zinc in the form
of zinc blende and related materials.
The method is applicable to gold contents from 0,5 g/t to 12 g/t.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreements based on this International Standard are encouraged to investigate the possibility of
applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of
currently valid International Standards.
ISO 385-1:1984, Laboratory glassware — Burettes — Part 1: General requirements.
ISO 648:1977, Laboratory glassware — One-mark pipettes.
ISO 1042:1998, Laboratory glassware — One-mark volumetric flasks.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 4787:1984, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity.
ISO 9599:1991, Copper, lead and zinc sulfide concentrates — Determination of hygroscopic moisture in the analysis
sample — Gravimetric method.
3 Principle
Roasting of the concentrate at 450 °C and 600 °C to remove arsenic and sulfur, followed by decomposition in bromine-
aqua regia-hydrofluoric acid. Extraction of the gold into DIBK containing Aliquat 336 from an aqua regia medium and
determination by flame atomic absorption spectrometric at 242,8 nm.
4 Reagents
During the analysis, use only reagents of recognized analytical grade and water that complies with grade 2 of
ISO 3696.
4.1  Gold metal, minimum 99,99 % purity.
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ISO 15249:1998(E)
 (ρ 1,42 g/ml).
4.2 Nitric acid,
20
4.3  Hydrochloric acid, (ρ 1,16 g/ml to 1,19 g/ml).
20
4.4  Aqua regia
Mix three parts hydrochloric acid (4.3) and one part nitric acid (4.2) with three parts of water. Prepare freshly as
required.
4.5  Bromine liquid, 99,5 % m/m.
4.6  Hydrofluoric acid (ρ 1,19 g/ml).

20
WARNING — Even when diluted, hydrofluoric acid is extremely dangerous and harmful to the eyes and
skin: rubber gloves and goggles should be worn when using this acid. Hydrofluoric acid attacks glassware.
Care should be taken to minimize the time of acid contact with glassware. Use only in a mechanically
ventilated fume cupboard.
 (ρ 0,81 g/ml).
4.7 Di-iso butyl ketone
20
4.8  Aliquat 336 (methyl-trioctyl ammonium chloride).
4.9  1 % Aliquat 336 in di-iso butyl ketone
Add 1 ml of Aliquat 336 (4.8) to 99 ml of di-iso butyl ketone (4.7) and mix thoroughly.
4.10  Gold standard solutions
NOTE Standard solutions should be prepared at the same ambient temperature as that at which the determinations are to
be conducted.
4.10.1  Gold standard solution (1 000 μg/ml).
Weigh 0,100 0 g of gold metal (4.1) into a 50 ml beaker, add 10 ml aqua regia (4.4), cover and heat to dissolve the
gold. Wash and remove the cover, and evaporate to near dryness (do not allow to go to dryness otherwise gold will
precipitate). Cool, add 5 ml of hydrochloric acid (4.3) and transfer the solution quantitatively to a 100 ml volumetric
flask, dilute to volume with water and mix thoroughly.
4.10.2  Gold standard solution (100 μg/ml).
Pipette 10 ml of gold standard solution (4.10.1) into a 100 ml volumetric flask, add 5 ml of hydrochloric acid (4.3), dilute
to volume with water and mix thoroughly.
4.10.3  Gold standard solution (10 μg/ml).
Pipette 10 ml of gold standard solution (4.10.2) into a 100 ml volumetric flask, add 5 ml of hydrochloric acid (4.3),
dilute to volume with water and mix thoroughly.
This solution shall be freshly prepared.
4.11  Calibration solutions
NOTE Calibration solutions should be prepared at the same ambient temperature as that at which the determinations are
to be conducted.
To each of seven 125 ml separating funnels add 75 ml of water and 20 ml of aqua regia (4.4). Add from a burette (5.2)
0 ml, 1 ml, 2 ml, 3 ml, 4 ml, 5 ml and 6 ml of gold standard solution (4.10.3). Treat these solutions using the extraction
procedure given in 7.4.
These standards contain 0 μg, 10 μg, 20 μg, 30 μg, 40 μg, 50 μg and 60 μg of gold.
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5 Apparatus
Ordinary laboratory equipment plus the following.
5.1  Volumetric glassware, of class A complying with ISO 385-1, ISO 648 and ISO 1042 and used in accordance
with ISO 4787.
5.2  Burette, A grade, 10 ml capacity capable of being read to 0,02 ml.
5.3  Muffle furnace, capable of giving an adequate zone of uniform temperature between 450 °C and 600 °C. A
ventilated furnace is preferred.
5.4  Crucibles, porcelain, having a depth of 10 mm to 15 mm and a diameter of 60 mm to 75 mm.
5.5  Atomic absorption spectrometer (AAS), equipped with background correction and a glass bead, rather than
a flow spoiler, in the spray chamber. Scale expansion and a flow adjustable nebulizer are recommended.
–1
5.6  Centrifuge, capable of holding at least 15 ml tubes and revolving at 0,833 s (3 000 rpm).
5.7  Centrifuge tubes, 15 ml volume with caps. Polypropylene is suitable.
5.8  Separating funnels, of 125 ml capacity. Borosilicate glass with PTFE stopcocks are recommended.
6 Sample
6.1 Test sample
Prepare an air-equilibrated test sample in accordance with ISO 9599.
NOTE A test sample is not required if predried test portions are to be used (see annex A).
6.2 Test portion
Taking multiple increments, extract a test portion from the test sample in such a manner that it is representative of
the whole contents of the dish or tray. Weigh, to the nearest 0,1 mg, approximately 5 g of the test sample. At the
same time as the test portion is weighed, weigh test portions for the level of hygroscopic moisture in accordance
with ISO 9599.
Alternatively, the method specified in annex A may be used to prepare predried test portions directly from the
laboratory sample.
7 Procedure
7.1 Number of determinations
Carry out the determinations at least in duplicate, and as far as possible under repeatability conditions, on each test
sample.
NOTE Repeatability conditions exist where mutually independent test results are obtained with the same method on
identical test material in the same laboratory by the same operator using the same equipment within short intervals of time.
7.2 Blank test
Carry out a blank test in parallel with the analysis using all reagents specified in the determination but omitting the
test portion. The purpose of the blank test in this method is to check the quality of the reagents. If a significant blank
value is obtained as a result of the blank test, check all reagents and rectify the problem.
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7.3 Decomposition of test portion
Transfer the test portion to a porcelain crucible and place in the muffle furnace (5.3) at 450 C and heat for 2 h.
°
Raise the muffle furnace temperature to 600 °C and continue heating for 1 h.
Remove the crucible from the furnace, cool, and transfer the roasted test portion to a 250 ml conical beaker.
Add 10 ml of water, swirl to form a slurry and add 2 ml of bromine (4.5) and mix. Cover with a watchglass, swirl to mix
and allow to stand at room temperature for 15 min.
Add 15 ml of hydrochloric acid (4.3) and digest on a hotplate at 90 °C until fumes of bromine are expelled. Continue the
digestion for 30 min. Remove from the hotplate and cool.
Remove the watchglass and rinse the underside with a minimum of water, collecting the washings in the conical
beaker. Carefully add 10 ml of nitric acid (4.2) and 1 ml of hydrofluoric acid (4.6). Return the beaker to the hotplate
and gently evaporate to near dryness.
NOTE Do not allow the digestion mixture to go to dryness, as gold will be lost.
Rinse the sides of the beaker with a minimum of water, add 20 ml of aqua regia (4.4), cover with the watchglass,
return to the hotplate and heat gently for 10 min. Remove from the hotplate and cool.
7.4 Extraction
Transfer the test solution to a 125 ml separating funnel (5.8), add sufficient water to make the volume to 100 ml and
swirl to mix.
Add 8 ml of 1
...