SIST ISO 10258:2018

INTERNATIONAL ISO
STANDARD 10258
Third edition
2018-02
Copper sulfide concentrates —
Determination of copper content —
Titrimetric methods
Concentrés de sulfure de cuivre — Dosage du cuivre — Méthodes
titrimétriques
Reference number
ISO 10258:2018(E)
©
ISO 2018

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ISO 10258:2018(E)

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ISO 10258:2018(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Method 1 (Long iodide method) . 1
4.2 Method 2 (Short iodide method). 1
5 Reagents . 2
6 Apparatus . 4
7 Sample . 4
7.1 Test sample . 4
7.2 Test portion . 4
8 Procedure. 4
8.1 Number of determinations . 4
8.2 Blank test . 5
8.3 Determination — Method 1: Long iodide method . 5
8.3.1 Decomposition of test portion . 5
8.3.2 Separation of copper . 5
8.3.3 Dissolution of copper precipitate . 6
8.3.4 Titration. 6
8.3.5 FAAS determination of copper in the insoluble residue, filtrate, and filter paper . 6
8.4 Determination — Method 2: Short iodide method . 7
8.4.1 Decomposition of the test portion . 7
8.4.2 Titration. 7
9 Expression of results . 8
10 Precision . 8
10.1 Expression of precision . 8
10.2 Method for obtaining the final result (see Annex B) . 9
10.3 Precision between laboratories . 9
10.4 Check of trueness .10
11 Test report .11
Annex A (informative) Procedure for the preparation and determination of the mass of a
predried test portion .12
Annex B (normative) Flowsheet of the procedure for the acceptance of analytical values for
test samples .14
Annex C (informative) Derivation of precision formulae .15
Bibliography .20
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ISO 10258:2018(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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 183, Copper, lead, zinc and nickel ores and
concentrates.
This third edition cancels and replaces the second edition (ISO 10258:2015), of which it is a minor
revision. Table C.1, Table C.2, Figure C.2 and Figure C.3 have been revised to correct the following
editorial errors:
— Table C.1 title, replaced ‘concentrated’ with ‘concentrate’.
— Table C.2 title, replaced ‘silver’ with ‘copper’.
— Table C.2 list at the bottom of the table, replaced ‘silver’ with ‘copper’.
— Figure C.2 title, replaced ‘silver’ with ‘copper’.
— Figure C.3 title, replaced ‘silver’ with ‘copper’.
— Annex A heading changed to ‘informative’.
— Annex B heading changed to ‘normative’.
In addition, the following editorial changes have been made:
— Clause 3, Terms and definitions, inserted.
— 10.4 NOTE changed to body text.
— References added for all formulae.
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INTERNATIONAL STANDARD ISO 10258:2018(E)
Copper sulfide concentrates — Determination of copper
content — Titrimetric methods
1 Scope
This document specifies two titrimetric methods for the determination of the copper content of copper
sulfide concentrates in the range 15 % (m/m) to 50 % (m/m), using sodium thiosulfate after separation
(method 1) or without separation (method 2) of copper from interfering elements.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 4787, Laboratory glassware — Volumetric instruments — Methods for testing of capacity and for use
ISO 9599, Copper, lead, zinc and nickel sulfide concentrates — Determination of hygroscopic moisture
content of the analysis sample — Gravimetric method
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Principle
4.1 Method 1 (Long iodide method)
A test portion is decomposed in nitric and sulfuric acids, and arsenic, antimony and tin are removed
by treatment with hydrobromic acid. Copper is separated from interfering elements by precipitation
of copper sulfide with sodium thiosulfate. The precipitate is dissolved in nitric and sulfuric acids,
ammonium hydrogen difluoride is added to eliminate interference of residual iron, and excess
potassium iodide is also added. Free iodine isolated by reaction between iodide ions and copper(II) ions
is titrated with sodium thiosulfate using soluble starch as the indicator.
4.2 Method 2 (Short iodide method)
A test portion is decomposed in nitric and sulfuric acids, and arsenic, antimony and tin are removed by
treatment with hydrobromic acid. Ammonium hydrogen difluoride is added to eliminate interference
of iron, and excess potassium iodide is also added. Free iodine isolated by reaction between iodide ions
and copper(II) ions is titrated with sodium thiosulfate using soluble starch as the indicator.
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ISO 10258:2018(E)

5 Reagents
During the analysis, use only reagents of recognized analytical grade and distilled water or water of
equivalent purity.
5.1 Copper metal, minimum purity 99,99 %.
5.2 Potassium iodide.
5.3 Ammonium hydrogen difluoride.
5.4 Sulfuric acid, diluted 1 + 1.
Slowly add 500 ml of concentrated sulfuric acid (ρ 1,84 g/ml) to 500 ml of water, while stirring and
20
cooling.
5.5 Sulfuric acid, diluted 1 + 999.
Add 1 ml of dilute sulfuric acid (5.4) to 500 ml of water.
5.6 Nitrit acid, concentrated (ρ 1,42 g/ml).
20
5.7 Nitrit acid, diluted 1 + 1.
Slowly add 500 ml of concentrated nitric acid (5.6) to 500 ml of water.
5.8 Hydrofluoric acid (ρ 1,14 g/ml).
20
5.9 Bromine.
5.10 Bromine water, saturated.
5.11 Hydrobromic acid (ρ 1,50 g/ml).
20
5.12 Acetic acid, diluted 1 + 3.
Slowly add 25 ml of glacial acetic (ρ 1,05 g/ml) to 75 ml of water.
20
5.13 Nitration mixture.
Slowly add 250 ml of concentrated sulfuric acid (ρ 1,84 g/ml) to 250 ml of concentrated nitric acid (5.6).
20
5.14 Ammonium hydrogen difluoride, 250 g/l solution.
5.15 Sodium carbonate, 20 g/l solution.
5.16 Sodium thiosulfate pentahydrate, 200 g/l solution.
5.17 Potassium thiocyanate, 100 g/l solution.
5.18 Starch, 2 g/l solution.
Moisten 1 g of soluble starch with cold water, slowly pour into 500 ml of hot water while stirring, and
boil for about 1 min.
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ISO 10258:2018(E)

5.19 Ethanol.
5.20 Standard solutions.
Standard solutions should be prepared at the same ambient temperature as that at which the
determinations will be conducted.
5.20.1 Sodium thiosulfate, standard volumetric solution (20 g/l).
5.20.1.1 Preparation
Dissolve 20 g of sodium thiosulfate (pentahydrate) in 1 l of freshly boiled and cooled water. Add 0,2 g of
sodium carbonate, stir to dissolve and allow to stand for at least one day. Standardize this solution as
specified in 5.20.1.2.
5.20.1.2 Standardization
Clean a piece of copper metal (5.1) by immersing it in warm dilute acetic acid (5.12). Wash the copper
thoroughly with water followed by ethanol (5.19) and allow to dry in air. Weigh into three separate
400 ml conical beakers to the nearest 0,1 mg, a mass of clean copper metal which approximates the
copper content in the test portion. Record these masses as m , m , and m .
1 2 3
Dissolve the copper using 10 ml of dilute nitric acid (5.7) followed by 5 ml of dilute sulfuric acid (5.4).
Heat to evaporate to dryness. Add 40 ml of water, heat to dissolve the soluble salts, and cool. Continue
the standardization as specified in 8.3.4 for method 1 and in 8.4.2 for method 2. Record the volumes of
sodium thiosulfate solution used in the titration as V , V , and V .
1 2 3
The standardization factor of the standard volumetric solution varies with the volume of sample
solution, mass of potassium iodide, mass of copper, and temperature of solution. The same volume
of solution and mass of potassium iodide as those used for the standardization should be used for
the analysis of the test portion. The temperatures of standardization and determination should be
essentially the same.
Calculate the standardization factors f , f , and f using Formulae (1) to (3):
1 2 3
m
1
f = (1)
1
V
1
m
2
f = (2)
2
V
2
m
3
f = (3)
3
V
3
Calculate, to four significant figures, the mean standardization factor f for the sodium thiosulfate
−5
standard volumetric solution, provided that the range of the values of f , f , and f does not exceed 10
1 2 3
g Cu/ml. If this range is exceeded, repeat the standardization.
5.20.2 Copper, standard solution (0,1 mg/ml).
Weigh, to the nearest 0,1 mg, 0,1 g of copper metal (5.1) into a 200 ml beaker, decompose with 10 ml of
dilute nitric acid (5.7). Heat to remove nitrogen oxides, cool, and add about 50 ml of water. Transfer to
a 1 000 ml volumetric flask, fill up nearly to the mark with water, mix and cool to room temperature;
then fill up exactly to the mark and mix again.
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ISO 10258:2018(E)

6 Apparatus
Ordinary laboratory equipment and the following.
6.1 Volumetric glassware, of class A complying with ISO 385, ISO 648, and ISO 1042, and used in
accordance with ISO 4787.
6.2 Analytical balance, sensitive to 0,1 mg.
6.3 Platinum crucibles.
6.4 Atomic absorption spectrometer (AAS), with a copper hollow cathode lamp.
Instrumental conditions:
— Flame: air/acetylene;
— Wavelength: 324,7 nm.
6.5 Inductively coupled plasma (ICP) atomic emission spectrometer (optional).
7 Sample
7.1 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).
7.2 Test portion
Taking multiple increments, extract a test portion from the test sample as specified in Table 1 and
weigh to the nearest 0,1 mg. At the same time as test portions are being weighed for analysis, weigh test
portions for the determination of hygroscopic moisture in accordance with ISO 9599.
Alternatively, the method specified in Annex A can be used to prepare predried test portions directly
from the laboratory sample.
Table 1 — Recommended test portion masses
Copper content (presumed) Mass of test
% (m/m) portion
≥ < g
15 25 0,8
25 50 0,4
8 Procedure
8.1 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 10258:2018(E)

8.2 Blank test
Carry out a blank test in parallel with the analysis using the same quantities of all reagents but omitting
the test portion. The purpose of the blank test in this method is to check the quality of reagents. If a
significant blank titration value is obtained as a result of the blank test, check all reagents and rectify
the problem.
8.3 Determination — Method 1: Long iodide method
8.3.1 Decomposition of test portion
Transfer the test portion to a 400 ml conical beaker and moisten with 10 ml of water. Add 20 ml of
dilute nitric acid (5.7), cover with a watch glass and heat for about 10 min at 60 °C to 70 °C. Add 10 ml of
dilute sulfuric acid (5.4) and heat gradually to decompose the test portion.
After the completion of the initial reaction, rinse the underside of the watch glass with a minimum
volume of water, collecting the washings in the conical beaker. Continue heating until strong white
fumes are evolved, then cool.
If the residue appears dark (presence of carbon), slowly add a small amount of the nitration mixture
(5.13) to the hot solution until the solution becomes colourless or bluish and heat until strong white
fumes are evolved.
If decomposition of the deposited sulfur is insufficient, add 5 ml of nitric acid (5.6) and 1 ml of bromine
(5.9), and heat until strong white fumes are evolved.
Carefully add 5 ml of water and 10 ml of hydrobromic acid (5.11) and heat until strong white fumes are
evolved. Remove from the source of heat and cool. After addition of 5 ml of dilute sulfuric acid (5.4) and
10 ml of hydrobromic acid (5.11), heat until strong white fumes are evolved. Remove from the source of
heat and cool.
Add 80 ml of water, warm to dissolve soluble salts, and heat until boiling. Filter through a medium
porosity filter paper, wash well with hot water, and collect the filtrate in a 400 ml conical beaker. Reserve
the filter paper and residue for the determination of copper by flame atomic absorption spectrometry
(FAAS) (as described in 8.3.5) unless it has been proven, through previous testing, that the copper in
the sample is completely soluble using the initial dissolution.
8.3.2 Separation of copper
Dilute the filtrate to 200 ml and heat to 70 °C to 90 °C, slowly add 40 ml of sodium thiosulfate solution
(5.16) while stirring, to produce a yellow or yellowish brown emulsion. Heat gradually and continue
boiling gently until the precipitate coagulates. Filter the solution through a medium porosity filter paper
and wash the filter paper and precipitate with hot water. Retain the filtrate for FAAS measurements of
copper (as described in 8.3.5).
Using water, rinse away the copper sulfide precipitate into the original conical beaker and decompose
the remaining precipitate on the filter paper using drop by drop addition of bromine water (5.10)
followed by nitric acid (5.6). Repeat this treatment as required, then wash well with hot water,
collecting this solution in the beaker containing the main precipitate. Retain the filter paper for FAAS
measurements of copper (as described in 8.3.5).
NOTE Instead of using the above step, the following method can be used: Transfer the precipitate and filter
paper into the original beaker, cover with a watch glass, and add 30 ml of nitration mixture (5.13). Heat slowly
to decompose the precipitate and the filter paper, and evaporate to dryness. Use more nitration mixture if the
residue appears dark. Continue heating strongly to destroy any elemental sulfur. After adding 10 ml of nitric
acid (5.6) around the top of the beaker to rinse away the residual sulfur, add 2 ml of dilute sulfuric acid (5.4) and
heat until strong white fumes are evolved. Remove from the heat source and cool. Add 40 ml of water, warm to
dissolve the soluble salts, and cool. Proceed to 8.3.4.
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ISO 10258:2018(E)

8.3.3 Dissolution of copper precipitate
Add 2 ml of dilute sulfuric acid (5.4) and 10 ml of nitric acid (5.6), heat slowly to decompose the
precipitate, and then evaporate to dryness. Continue heating strongly to destroy any elemental sulfur.
After adding 10 ml of nitric acid (5.6) around the top of the beaker to rinse away the residual sulfur, add
2 ml of dilute sulfuric acid (5.4), and heat until strong white fumes are evolved. Remove from the source
of heat and cool.
8.3.4 Titration
Add 40 ml of water, warm to dissolve the soluble salts, and cool the solution. Add sodium carbonate
solution (5.15) until the copper precipitate appears, then add dilute acetic acid (5.12) until the copper
precipitate disappears and an excess of 3 ml to 5 ml. Add 1 ml of ammonium hydrogen difluoride
solution (5.14) and swirl. Add 15 g of potassium iodide (5.2), swirl to dissolve, and immediately titrate
with sodium thiosulfate standard volumetric solution (5.20.1). When the yellow brown iodine colour
fades to a pale yellow, add 5 ml of starch solution (5.18) as the indicator.
NOTE 1 Instead of using the above step, the following method can be used: Add 3 g of potassium iodide (5.2),
swirl to dissolve, and immediately titrate with sodium thiosulfate standard volumetric solution (5.20.1). When
the yellow brown iodine colour fades to a pale yellow, add 5 ml of starch solution (5.18) as the indicator, and
continue the titration until the colour of the solution becomes light blue. Then add 5 ml of potassium thiocyanate
solution (5.17).
NOTE 2 The presence of Ag, Bi, Hg, and Pb can obscure the colour change. In this case, add the starch solution
(5.18) earlier in the titration, when the solution is a light brown colour.
Continue the titration until the blue indicator colour just disappears. Record the volume, V, of sodium
thiosulfate standard volumetric solution used in the titration.
8.3.5 FAAS determination of copper in the insoluble residue, filtrate, and filter paper
8.3.5.1 Decomposition of the insoluble residue
Place the retained residue and the filter paper in a platinum crucible (6.3), dry, and ignite at 750 °C to
800 °C. Allow the crucible to cool, add 5 ml of dilute sulfuric acid (5.4) and 5 ml to 10 ml of hydrofluoric
acid (5.8), heat to evaporate almost to dryness, and volatilize the silicon as silicon tetrafluoride. Dissolve
with a small quantity of water and 1 ml of dilute sulfuric acid (5.4) by heating. Proceed to 8.3.5.3.
8.3.5.2 Decomposition of the precipitate remaining on the filter paper
Transfer the retained filter paper into a beaker and add 30 ml of nitration mixture (5.13). Heat to
evaporate to dryness. If the residue appears dark (presence of carbon), repeat this step. Dissolve with a
small quantity of water and 1 ml of dilute sulfuric acid (5.4) by heating. Proceed to 8.3.5.3.
8.3.5.3 Spectrometric measurement
Transfer the solutions prepared in 8.3.5.1, 8.3.5.2, and the retained filtrate from 8.3.2 into a 500 ml
volumetric flask and make up to the mark with water.
Prepare calibration solutions by adding, from a pipette or a micro-burette, 0,0 ml, 0,50 ml, 1,00 ml,
1,50 ml, 2,00 ml, and 3,00 ml of copper standard solution (5.20.2) into a series of 200 ml one-mark
volumetric flasks, add 1 ml of dilute sulfuric acid (5.4) to each one, and make up to the marks with water.
Aspirate the test solution and the calibration solutions into the atomic absorption spectrometer (6.4)
using an air/acetylene flame and a wavelength of 324,7 nm with background correction.
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ISO 10258:2018(E)

Prepare a calibration graph of masses of copper in the calibration solutions versus absorbances and
read the mass, in micrograms, of copper in the test solution from the calibration graph.
NOTE Alternatively, the ICP atomic emission spectrometer (6.5) can be used for the determination of copper
at a wavelength of 324,7 mm.
Calculate the mass of copper in the residue and filtrate using Formula (4):
−6
mm=×10 (4)
45
where
m is the mass, in grams, of copper in the insoluble residue, the precipitate remaining on the
4
filter paper, and the filtrate;
m is the mass, in micrograms, of copper in the test solution.
5
8.4 Determination — Method 2: Short iodide method
8.4.1 Decomposition of the test portion
Transfer the test portion to a 400 ml conical beaker and moisten with 10 ml of water. Add 20 ml of
dilute nitric acid (5.7), cover with a watch glass, and heat for about 10 min at 60 °C to 70 °C. Add 10 ml of
dilute sulfuric acid (5.4) and heat gradually to decompose the test portion.
After completion of the initial reaction, rinse the underside of the watch glass with a minimum volume
of water, collecting the washings in the conical beaker. Continue heating until strong white fumes are
evolved, then cool.
If the residue appears dark (presence of carbon), slowly add a small amount of the nitration mixture
(5.13) to the hot solution until the solution becomes colourless or bluish and heat until strong white
fumes are evolved.
If decomposition of the deposited sulfur is insufficient, add 5 ml of nitric acid (5.6), 1 ml of bromine
(5.9), and 2 ml of dilute sulfuric acid (5.5), and heat until strong white fumes are evolved.
Carefully add 5 ml of water, 10 ml of hydrobromic acid (5.11), and 5 ml of dilute sulfuric acid (5.4), and
heat until strong white fumes are evolved. Remove from the source of heat and cool. Add 5 ml of dilute
sulfuric acid (5.4) and 10 ml of hydrobromic acid (5.11), and heat until strong white fumes are evolved.
Continue heating to evaporate to complete dryness and then cool.
If it has not been proven, through previous testing, that the copper in the sample is completely soluble
using the initial dissolution described above, the following procedure should be carried out. Add 20 ml
of water, warm to dissolve soluble salts, then heat until boiling. Filter through a medium-porosity filter
paper, wash well with hot water collecting the filtrate and washings in a 400 ml conical beaker, and
then heat to evaporate to dryness. Determine the copper content of the insoluble residue in accordance
with 8.3.5.
8.4.2 Titration
Add 40 ml of dilute sulfuric acid (5.5), warm to dissolve the sol
...