ISO 12739:2006

INTERNATIONAL ISO
STANDARD 12739
Second edition
2006-07-01
Zinc sulfide concentrates —
Determination of zinc —
Ion-exchange/EDTA titrimetric method
Concentrés sulfurés de zinc — Dosage du zinc — Méthode par échange
d'ions et titrage à l'EDTA
Reference number
©
ISO 2006
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ii ISO 2006 – All rights reserved

Contents Page
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus . 3
6 Sample . 3
6.1 Test sample . 3
6.2 Test portion . 3
7 Procedure . 3
7.1 Number of determinations . 3
7.2 Blank test . 4
7.3 Dissolution of test portion . 4
7.4 Preparation of the ion-exchange column . 4
7.5 Adsorption of zinc on ion-exchange column . 5
7.6 Elution of zinc from ion-exchange column . 5
7.7 Titration . 5
7.8 Determination of the titration factor of the EDTA standard volumetric solution . 5
8 Expression of results . 6
9 Precision . 7
9.1 Expression of precision . 7
9.2 Procedure for obtaining the final result . 7
9.3 Between-laboratories precision . 7
9.4 Check of trueness . 8
10 Test report . 9
Annex A (normative) Ion-exchange resins and columns . 10
Annex B (normative) Procedure for the preparation and determination of the mass of a predried test
portion . 12
Annex C (normative) Determination of cadmium by atomic absorption spectrometry . 14
Annex D (normative) Flowchart of the procedure for the acceptance of analytical values for test
samples . 16
Annex E (informative) Effect of potentially interfering elements . 17
Annex F (informative) Derivation of precision equations . 18
Bibliography . 23
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ISO 2006 – All rights reserved iii

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO12739 was prepared by Technical Committee ISO/TC183, Copper, lead, zinc and nickel ores and
concentrates.
This second edition cancels and replaces the first edition (ISO 12739:1997), which has been technically
revised.
©
iv ISO 2006 – All rights reserved

INTERNATIONAL STANDARD ISO 12739:2006(E)
Zinc sulfide concentrates — Determination of zinc —
Ion-exchange/EDTA titrimetric method
WARNING — This International Standard may involve hazardous materials, operations and equipment.
It is the responsibility of the user of this International Standard to establish appropriate health and
safety practices and determine the applicability of regulatory limitations prior to use.
1Scope
This International Standard specifies an ion-exchange/EDTA titrimetric method for the determination of the
mass fraction of zinc in zinc concentrates. The method is applicable to zinc sulfide concentrates having a mass
fraction of zinc in the range from 11 % to 62 %.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 385, Laboratory glassware — Burettes
ISO 648, Laboratory glassware — One-mark pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 4787, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity
ISO 9599, Copper, lead and zinc sulfide concentrates — Determination of hygroscopic moisture in the analysis
sample — Gravimetric method
3 Principle
The test portion of zinc concentrate is dissolved in hydrochloric, nitric and sulfuric acids. The acidity is adjusted
to about 2 mol/l with respect to hydrochloric acid. Zinc is adsorbed on a strongly basic anion-exchange resin.
2 mol/l
Some interfering ions are removed by elution with dilute hydrochloric acid. Zinc is eluted with an
ammonia/ammonium chloride solution. Zinc is determined in the eluate by titration with EDTA at a pH of
approximately 5,6 using xylenol-orange indicator.
4Reagents
During the analysis, only reagents of recognized analytical grade and water that complies with grade 2 of
ISO 3696 shall be used.
4.1 Zinc, 99,99 % minimum purity, free from oxide prior to use.
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ISO 2006 – All rights reserved 1

The surface of the metal may be cleaned by immersing the metal in hydrochloric acid (4.3) diluted 1 + 9, for
◦
1 min, then washed well with water followed by an acetone rinse and dried in an oven at 50 C.
4.2 Xylenol-orange indicator ()0,1 % m/m
Mix 0,1 g of the sodium salt of xylenol orange with 100 g of potassium nitrate crystals by gently grinding in a
ceramic mortar with a pestle. Mixing is considered complete when the colour is uniform throughout.
4.3 Hydrochloric acid (ρ 1,16 g/ml to 1,19 g/ml)
4.4 Hydrochloric acid, diluted (1 + 1)
Add 500 ml of hydrochloric acid (4.3) to 500 ml of water.
4.5 Hydrochloric acid, diluted (1 + 5)
Add 100 ml of hydrochloric acid (4.3) to 500 ml of water.
4.6 Nitric acid ()ρ 1,42 g/ml
4.7 Nitric acid, diluted (1 + 1)
Add 500 ml of nitric acid (4.6) to 500 ml of water.
4.8 Sulfuric acid, diluted (1 + 1)
Add carefully and slowly, while stirring, 500 ml of sulfuric acid (ρ 1,84 g/ml) to 500 ml of water.
4.9 Sulfuric acid, diluted (1 + 100)
Add 20 ml of dilute sulfuric acid (4.8) to 1 000 ml of water.
4.10 Hydrofluoric acid (ρ 1,13 g/ml to 1,15 g/ml)
4.11 Ammonia solution, diluted (7 + 100)
Add 70 ml of aqueous ammonia solution (ρ 0,89 g/ml) to 1 000 ml of water.
4.12 Ammonia/ammonium chloride solution
Dissolve 20 g of ammonium chloride in 1l of dilute ammonia solution (4.11).
4.13 Hydrochloric acid/ascorbic acid solution
Dissolve 0,25 g of ascorbic acid in 100 ml of dilute hydrochloric acid (4.5). Prepare fresh on the day of use.
4.14 Ammonium fluoride solution ()50 g/l
Dissolve 50 g of ammonium fluoride in water and dilute to 1l.
4.15 Sodium thiosulfate solution ()
100 g/l
Dissolve 100 g of sodium thiosulfate pentahydrate in water and dilute to 1l.
4.16 Buffer solution ()pH = 5,5
Dissolve 250 g of ammonium acetate and 25 ml of concentrated acetic acid (ρ 1,05 g/ml) in water and dilute
to .1l
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2 ISO 2006 – All rights reserved

4.17 Para-nitrophenol indicator solution ()2 g/l
Dissolve 0,2 g of para-nitrophenol in water and dilute to 100 ml.
4.18 EDTA standard volumetric solution ()0,1 mol/l
Dissolve 37,2 g of the di-sodium salt of ethylenediaminetetraacetic acid dihydrate (EDTA) in water and dilute to
.
1l
5 Apparatus
5.1 Class A volumetric glassware complying with ISO 385, ISO 648 and ISO 1042, and used in accordance
with ISO 4787.
5.2 Balance, capable of being read to 0,1 mg.
5.3 Laboratory hotplate
◦
5.4 Muffle furnace, capable of operating at 800 C.
5.5 Platinum crucibles, of capacity 25 ml.
5.6 Ion exchange columns, having typical dimensions as shown in Annex A.
6Sample
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 B).
6.2 Test portion
Taking multiple increments, extract a test portion of 0,5 g, weighed to the nearest 0,1 mg, from the test sample,
in such a manner that it is representative of the contents of the dish or tray. At the same time as the test portion
is weighed, weigh test portions for the determination of hygroscopic moisture in accordance with ISO 9599.
Alternatively, the method specified in Annex B 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, 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.
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ISO 2006 – All rights reserved 3

7.2 Blank test
Determine a reagent blank. It is advisable to perform duplicate blank determinations every time an analysis is
carried out on a laboratory sample. The blank samples are carried through the whole procedure, apart from
where no laboratory sample test portion is required. The volume of EDTA titrant used is V .
b
7.3 Dissolution of test portion
Place the test portion in a 300 ml conical beaker. Add 25 ml of hydrochloric acid (4.3). Cover with a watch glass
and heat the beaker and contents gently for 5 min.
Add 20 ml of dilute nitric acid
...