ISO 12744:2025

International
Standard
ISO 12744
Third edition
Copper, lead, zinc and nickel
2025-03
concentrates — Experimental
methods for checking the precision
of sampling
Concentrés de cuivre, de plomb, de zinc et de nickel — Méthodes
expérimentales de contrôle de la fidélité de l'échantillonnage
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 General conditions . 2
5.1 General .2
5.2 Number of lots .2
5.3 Number of increments and number of samples .2
5.4 Sample processing and analysis.3
5.5 Frequency of precision checks .3
6 Method of experiment . 3
6.1 Interleaved samples .3
6.2 Sample processing and analysis.4
6.2.1 General .4
6.2.2 Sample processing method 1 .5
6.2.3 Sample processing method 2 .5
6.2.4 Sample processing method 3 .6
7 Evaluation of experimental data . 7
7.1 General .7
7.2 Sample processing method 1 .7
7.3 Sample processing method 2 .8
7.4 Sample processing method 3 .10
8 Assessment of results and action .11
8.1 General .11
8.2 Sampling .11
8.3 Sample processing .11
8.4 Analysis .11
9 Recording of data .11
Annex A (informative) Recording of sampling data .12
Bibliography .16

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
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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this may not represent the latest information, which may be obtained from the patent database available at
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related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see 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 12744:2006), which has been technically
revised.
The main changes are as follows:
— the precisions of sampling, sample preparation and measurement are now estimated from the mean
squared differences between duplicates rather than simply the mean differences, which provides a
better unbiased estimate of precision.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 12744:2025(en)
Copper, lead, zinc and nickel concentrates — Experimental
methods for checking the precision of sampling
WARNING — This document can involve hazardous materials, operations and equipment. It is the
responsibility of the user of this document to establish appropriate health and safety practices and
determine the applicability of regulatory limitations prior to use.
1 Scope
This document specifies methods for checking the precision of primary sampling, sample processing,
chemical analysis, physical testing and determination of moisture content of copper, lead, zinc and nickel
concentrates being carried out in accordance with the methods specified in ISO 12743, expressed in terms of
standard deviations.
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 10258, Copper sulfide concentrates — Determination of copper content — Titrimetric methods
ISO 11441, Lead sulfide concentrates — Determination of lead content — Back titration of EDTA after
precipitation of lead sulfate
ISO 12743, Copper, lead, zinc and nickel concentrates — Sampling procedures for determination of metal and
moisture content
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
k number of lots
n number of increments
R absolute difference between duplicates for interleaved samples A and B
R absolute difference between means for divided interleaved samples A and A , and B and B
2 1 2 1 2
R absolute difference between means for interleaved sample A and interleaved sample B
s estimated value of standard deviation, σ

2 2
s estimated variance from R
1 1
2 2
s estimated variance from R
2 2
2 2
s estimated variance from R
3 3
s estimated standard deviation of analysis
A
s estimated standard deviation of sample processing
P
s estimated standard deviation of sampling
S
s estimated standard deviation of sampling and sample processing
SP
s estimated total standard deviation of sampling, sample processing and analysis
T
x first duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B
i1
x second duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample
i2
A or B
x first duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A
ij1
or B, and j = 1 or 2 and indicates laboratory samples A or A , and B or B
1 2 1 2
x second duplicate result for sample, where i = 1 and 2 and indicates interleaved sample A or B, and
ij2
j = 1 or 2 and indicates laboratory samples A or A , and B or B
1 2 1 2
x
mean value of duplicate results
mean of mean value of duplicate results
x
mean of x values, and grand mean for sample processing method 3
x
grand mean of all results for sample processing methods 1 and 2
x
5 General conditions
5.1 General
The determination of precision of primary sampling is based on collecting pairs of interleaved samples from
each lot. If sample processing and measurement are also carried out in duplicate, it is possible to determine
the precision of sample processing and analysis.
5.2 Number of lots
It is recommended that pairs of interleaved samples should be collected from more than 20 lots of the same
type of concentrate, in order to reach a reliable conclusion. The lot size shall be chosen to ensure that more
than 20 lots are available for the precision determination.
5.3 Number of increments and number of samples
The minimum number of increments for checking precision should preferably be twice the number
determined in accordance with ISO 12743. Hence, if the number of increments required for routine sampling
is n and one lot sample is constituted, the minimum number of increments should be 2n, and two interleaved
samples shall be constituted.
Alternatively, if the precision is being checked as part of routine sampling, n increments may be taken and
two interleaved samples constituted, each comprising n/2 increments. The sampling precision thus obtained
shall be divided by 2 to obtain the sampling precision for lot samples comprising n increments.
5.4 Sample processing and analysis
Sample processing shall be carried out in accordance with ISO 12743. The analysis of samples shall be
carried out according to the methods specified in the relevant International Standards, such as ISO 10258,
ISO 11441 and ISO 12739.
5.5 Frequency of precision checks
It is recommended that, even after a precision check has been conducted, further checks should be carried
out at regular intervals. Precision checks should also be carried out when there is a change in equipment.
Because of the large amount of work involved in checking precision, it is recommended that checks should
be carried out as a part of routine sampling and analysis.
6 Method of experiment
6.1 Interleaved samples
Each alternate primary increment shall be diverted so that pairs of interleaved samples A and B are formed.
The number of divided increments per primary increment should be the same as for routine sampling. An
example of a sampling plan for producing pairs of interleaved samples A and B is shown in Figure 1.

Figure 1 — Example of a plan for interleaved duplicate sampling
6.2 Sample processing and analysis
6.2.1 General
The pairs of interleaved samples A and B taken in accordance with 6.1 shall be divided separately and subjected
to method 1, method 2 or method 3 sample processing and analysis as described in 6.2.2, 6.2.3 or 6.2.4.

6.2.2 Sample processing method 1
The two interleaved samples A and B shall be divided separately to prepare four laboratory samples: A , A ,
1 2
B and B . These laboratory samples shall each be analysed in duplicate, and the duplicates designated as
1 2
follows:
— x and x for sample A ;
111 112 1
— x and x for sample A ;
121 122 2
— x and x for sample B ;
211 212 1
— x and x for sample B .
221 222 2
See Figure 2.
The eight determinations shall be run in random order, by the same analyst on the same day using
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