Steel and iron -- Determination of nickel content -- Gravimetric or titrimetric method

ISO 4938:2016 specifies a method for the determination of nickel in steel and iron by gravimetry or titrimetry. The method is applicable to nickel contents from 1 % to 30 % (mass fraction).

Aciers et fontes -- Détermination du nickel -- Méthode gravimétrique ou titrimétrique

ISO 4938:2016 spécifie une méthode gravimétrique ou titrimétrique de détermination du nickel dans les aciers et les fontes. La méthode est applicable aux teneurs en nickel comprises entre 1 % et 30 % (fraction massique).

General Information

Status
Published
Publication Date
01-Feb-2016
Current Stage
9060 - Close of review
Start Date
05-Jun-2021
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INTERNATIONAL ISO
STANDARD 4938
Second edition
2016-02-01
Steel and iron — Determination of
nickel content — Gravimetric or
titrimetric method
Aciers et fontes — Détermination du nickel — Méthode gravimétrique
ou titrimétrique
Reference number
ISO 4938:2016(E)
ISO 2016
---------------------- Page: 1 ----------------------
ISO 4938:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4938:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Principle ........................................................................................................................................................................................................................ 1

4 Reagents ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 4

6 Sampling ........................................................................................................................................................................................................................ 5

7 Procedure..................................................................................................................................................................................................................... 5

7.1 Test portion ................................................................................................................................................................................................ 5

7.2 Determination ......................................................................................................................................................................................... 5

7.2.1 Preparation of the test solution .......................................................................................................................... 5

7.2.2 First nickel precipitation ........................................................................................................................................... 5

7.2.3 Second nickel precipitation .................................................................................................................................... 6

7.2.4 Gravimetric determination ..................................................................................................................................... 7

7.2.5 Titrimetric determination ....................................................................................................................................... 7

8 Expression of results ........................................................................................................................................................................................ 8

8.1 Methods of calculation ..................................................................................................................................................................... 8

8.1.1 Gravimetric determination ..................................................................................................................................... 8

8.1.2 Titrimetric determination ....................................................................................................................................... 8

8.2 Precision ....................................................................................................................................................................................................... 8

9 Test report ................................................................................................................................................................................................................... 9

Annex A (informative) Additional information on the international interlaboratory test.......................10

Annex B (informative) Graphical representation of precision data .................................................................................11

Annex C (normative) Determination of nickel in combined filtrates by atomic

absorption spectrometry ..........................................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................16

© ISO 2016 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 4938:2016(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.

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

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information.

The committee responsible for this document is ISO/TC 17, Steel, Subcommittee SC 1, Methods of

determination of chemical composition.

This second edition cancels and replaces the first edition (ISO 4938:1988), which has been

technically revised.
iv © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 4938:2016(E)
Steel and iron — Determination of nickel content —
Gravimetric or titrimetric method
1 Scope

This International Standard specifies a method for the determination of nickel in steel and iron by

gravimetry or titrimetry.
The method is applicable to nickel contents from 1 % to 30 % (mass fraction).
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 4793, Laboratory sintered (fritted) filters — Porosity grading, classification and designation

ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical

composition
3 Principle
Dissolution of a test portion with appropriate acids.
Precipitation of the nickel as nickel-dimethylglyoxime.
— Cobalt, if present, is oxidized by potassium hexacyanoferrate(lll).

— Copper, if present with cobalt, preferably is removed by controlled potential electrolysis.

Acid dissolution of the precipitate and filtration of the solution, followed by a second precipitation of

the nickel as nickel dimethylglyoxime.

In the case of the gravimetric determination, weighing the dried dimethylglyoxime precipitate.

In the case of the titrimetric determination, acid dissolution of the precipitate, addition of excess EDTA.Na

solution and back titration of the excess EDTA.Na by zinc solution using xylenol orange as an indicator.

In both cases, determination of residual nickel in the filtrate(s) by atomic absorption spectrometry

(see Annex C).
4 Reagents

During the analysis, unless otherwise specified, use only reagents of recognized analytical grade and

only distilled grade 2 water as specified in ISO 3696 or water of equivalent purity.

4.1 Sodium hydrogen sulphate (NaHSO ).
© ISO 2016 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 4938:2016(E)
4.2 Ethanol, 95 % (volume fraction).
4.3 Acetic acid, glacial, ρ approximately 1,05 g/ml.
4.4 Hydrofluoric acid, ρ approximately 1,15 g/ml.

WARNING — Hydrofluoric acid is extremely irritating and corrosive to skin and mucous

membranes producing severe skin burns which are slow to heal. In case of contact with skin,

wash well with water, apply a topical gel containing 2,5 % (mass fraction) calcium gluconate and

seek immediate medical treatment.
4.5 Nitric acid, ρ approximately 1,40 g/ml.
4.6 Perchloric acid, ρ approximately 1,54 g/ml.

WARNING — Perchloric acid vapour can cause explosions in the presence of ammonia, nitrous

fumes or organic material in general.
4.7 Sulphuric acid, ρ approximately 1,84 g/ml.
4.8 Ammonia solution, ρ approximately 0,90 g/ml.
4.9 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted 1 + 1.
Add 500 ml of hydrochloric acid (ρ approximately 1,19 g/ml) to 500 ml of water.
4.10 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted 1 + 99.
Add 10 ml of hydrochloric acid (ρ approximately 1,19 g/ml) to 990 ml of water.
4.11 Nitric acid, ρ approximately 1,40 g/ml, diluted 2 + 3.
Add 200 ml of nitric acid (4.5) to 300 ml of water.
4.12 Perchloric acid, ρ approximately 1,54 g/ml, diluted 1 + 49.
Add 10 ml of perchloric acid (4.6) to 490 ml of water.
4.13 Ammonia solution, ρ approximately 0,90 g/ml, diluted 1 + 1.
Add 500 ml of ammonia solution (4.8) to 500 ml of water.
4.14 Ammonia solution, ρ approximately 0,90 g/ml, diluted 1 + 3.
Add 100 ml of ammonia solution (4.8) to 300 ml of water.
4.15 Hydrochloric/nitric acids mixture.

Mix three volumes of hydrochloric acid (ρ approximately 1,19 g/ml) with one volume of nitric acid (4.5).

Prepare this mixture immediately prior to use.
4.16 Ammonium acetate, 200 g/l solution.
2 © ISO 2016 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 4938:2016(E)
4.17 Ammonium citrate buffer solution.

Dissolve 500 g of citric acid monohydrate (C H O ·H O) in 675 ml of ammonia solution (4.8) and dilute

6 8 7 2
to 1 l with water.
Filter before use.
4.18 Citric acid, 500 g/l solution.

Dissolve 500 g of citric acid monohydrate (C H O ·H O) in water and dilute to 1 l with water.

6 8 7 2
Filter before use.
4.19 Dimethylglyoxime, 30 g/l solution in alkaline medium.

Dissolve 20 g of potassium hydroxide in 400 ml of water, add 30 g of dimethylglyoxime (C H N O ) and

4 8 2 2
stir until dissolution is complete. Dilute to 1 l with water and mix.
Filter before use.
4.20 Dimethylglyoxime, 10 g/l solution in ethanol.
Dissolve 10 g of dimethylglyoxime (C H N O ) in 1 000 ml of ethanol (4.2).
4 8 2 2
Filter before use.
4.21 Hydrazine dihydrogen sulphate (N H SO ), 100 g/l solution.
2 6 4
4.22 Potassium hexacyanoferrate(III), K [Fe(CN) ], 100 g/l solution.
3 6
This solution is stable for approximately 30 days.

1 ml of this solution corresponds approximately to 0,02 g of cobalt and manganese, respectively.

4.23 Washing water, adjusted to pH 8 with a few drops of ammonia solution (4.13).

4.24 Ethylenediaminetetraacetic acid disodium salt (EDTA.Na ), standard-volumetric solution.

4.24.1 Preparation of the solution

Dissolve 6,33 g of ethylenediaminetetraacetic acid disodium salt (C H O N Na ·2H O) in water,

10 14 8 2 2 2

transfer the solution to a 1 000 ml one-mark volumetric flask, dilute to the mark with water and mix.

1 ml of this standard solution corresponds approximately to 1 mg of nickel.
4.24.2 Standardization of the solution

Transfer 25,0 ml of the nickel standard solution (4.24.3) to a 250 ml beaker and add 33 ml of EDTA.Na

solution (4.24.1). Add 15 ml of ammonium acetate solution (4.16) and dilute to about 150 ml with water.

Continue as described in the third paragraph of 7.2.5.
© ISO 2016 – All rights reserved 3
---------------------- Page: 7 ----------------------
ISO 4938:2016(E)

The corresponding concentration, c, of the EDTA.Na solution (4.24.1), expressed in milligrams of nickel

per millilitre, is given by Formula (1):
mm×25 +×V
() ()
12 1
c = (1)
where

m is the mass of nickel contained in 1 ml of the nickel standard solution (4.24.3), in milligrams;

m is the mass of nickel corresponding to 1 ml of the zinc standard solution (4.25), in milligrams;

V is the volume of the zinc standard solution (4.25) used for the titration, in millilitres;

V is the volume of the EDTA.Na solution (4.24.1) used for the standardization, in millilitres.

2 2
4.24.3 Nickel standard solution

Weigh, to the nearest 0,1 mg, 1,000 g of nickel [Ni > 99,95 % (mass fraction)]. Dissolve in 20 ml of

nitric acid (4.11). Boil to remove nitrous fumes, cool, transfer quantitatively to a 1 000 ml one-mark

volumetric flask, dilute to the mark with water and mix.
1 ml of this standard solution contains 1,0 mg of nickel.
4.25 Zinc standard solution.

Weigh, to the nearest 0,1 mg, 1,114 0 g of zinc [purity > 99,9 % mass fraction] and transfer to a 300 ml

beaker. If the zinc is oxidized, it should be cleaned with hydrochloric acid (4.9), water and acetone, and

dried for 5 min at 110 °C before use.

Add about 50 ml of water, 20 ml of hydrochloric acid (4.9) and five drops of bromine-saturated water.

Cover with a watch glass and heat until the metal is completely dissolved. Continue the heating until the

colour of the bromine disappears, cool to room temperature and add 20 ml of glacial acetic acid (4.3).

Adjust the pH of the solution to 6,0 ± 0,2 with ammonia solution (4.14). Transfer quantitatively to a

1 000 ml one-mark volumetric flask, dilute to the mark with water and mix.

1 ml of this standard solution corresponds to 1,0 mg of Ni and also approximately to 1 ml of the

EDTA.Na standard volumetric solution (4.24).
4.26 Xylenol orange, 1 g/l solution.

Pulverize 0,1 g of xylenol orange (C H N O SNa ) with a little portion of water to make a paste.

31 28 2 13 4
Dilute to 100 ml with water. Filter and store in a brown glass stoppered bottle.
This solution is stable for one week.
5 Apparatus

All volumetric glassware shall be Class A in accordance with ISO 648 or ISO 1042, as appropriate.

Ordinary laboratory equipment and the following shall be used.
5.1 Sintered-glass filter, complying with porosity grade P16 of ISO 4793.
5.2 pH-meter.

5.3 Apparatus for controlled-potential electrolysis, with a saturated calomel reference electrode

and a platinum electrode.
4 © ISO 2016 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 4938:2016(E)
6 Sampling

Carry out sampling in accordance with ISO 14284 or appropriate national standards for steel and iron.

7 Procedure
7.1 Test portion

The test portion shall be selected so that the amount of nickel to be precipitated is within the range of

25 mg to 70 mg for the gravimetric determination and 25 mg to 40 mg for the titrimetric determination.

For example, if 3,5 % (mass fraction) nickel content is expected, weigh approximately a 1 g test portion.

All weighings shall be to the nearest 0,1 mg.
7.2 Determination
7.2.1 Preparation of the test solution

Place the test portion (7.1) in a beaker of suitable capacity (e.g. 400 ml for test portions up to 2,5 g and

600 ml for test portions above 2,5 g). Add 30 ml of hydrochloric/nitric acids mixture (4.15) for test

portions up to 2,5 g and 50 ml for other test portions. Cover the beaker with a watch-glass and heat at

50 °C to 60 °C until reaction is complete and then add 0,5 ml to 1 ml of hydrofluoric acid (4.4). Add 30 ml

of perchloric acid (4.6) for test portions up to 2,5 g and 50 ml for other test portions.

Increase the temperature to approximately 180 °C and evaporate the solution until copious white fumes

of perchloric acid are evolved.

Cover the beaker with a dry watch-glass and continue fuming until the chromium, if present, is

completely oxidized (at this stage, the solution gets the orange dichromate colour).

Remove the beaker from the heat source and allow to cool. Add 100 ml of water and heat to dissolve the

salts. Boil for about 5 min to eliminate chlorine compounds.

Filter through a rapid filter paper to remove graphite and oxides of silicon, tungsten, niobium and

tantalum. Collect the filtrate in an 800 ml beaker and wash eight to ten times with hot perchloric

acid (4.12) and then, wash twice with water.
NOTE This solution is the main solution.

Transfer the filter and residue to a platinum crucible. Dry, ash and ignite at a temperature of 900 °C.

Treat the residue with hydrofluoric acid (4.
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 4938
ISO/TC 17/SC 1 Secretariat: JISC
Voting begins on: Voting terminates on:
2013-12-12 2014-05-12
Steel and irons — Determination of nickel content —
Gravimetric or titrimetric method
Aciers et fontes — Dosage du nickel — Méthode gravimétrique ou titrimétrique
[Revision of first edition (ISO 4938:1988)]
ICS: 77.080.01
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for
Standardization (ISO), and processed under the ISO lead mode of collaboration
as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member
bodies for a parallel five month enquiry.

Should this draft be accepted, a final draft, established on the basis of comments

received, will be submitted to a parallel two-month approval vote in ISO and
THIS DOCUMENT IS A DRAFT CIRCULATED
formal vote in CEN.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
To expedite distribution, this document is circulated as received from the
IN ADDITION TO THEIR EVALUATION AS
committee secretariat. ISO Central Secretariat work of editing and text
BEING ACCEPTABLE FOR INDUSTRIAL,
composition will be undertaken at publication stage.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 4938:2013(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2013
---------------------- Page: 1 ----------------------
ISO/DIS 4938:2013(E)
Copyright notice

This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as

permitted under the applicable laws of the user’s country, neither this ISO draft nor any extract

from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means,

electronic, photocopying, recording or otherwise, without prior written permission being secured.

Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s

member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2013 – All rights reserved
---------------------- Page: 2 ----------------------
ISO DIS/4938
Contents Page

Foreword ............................................................................................................................................................iv

1  Scope......................................................................................................................................................1

2  Normative references............................................................................................................................1

3  Principle .................................................................................................................................................1

4  Reagents ................................................................................................................................................2

5  Apparatus...............................................................................................................................................4

6  Sampling ................................................................................................................................................5

7  Procedure...............................................................................................................................................5

8  Expression of results............................................................................................................................8

9  Test report..............................................................................................................................................9

Annex A (informative) Additional information on the international co-operative tests.............................11

Annex B (informative) Graphical representation of precision data...................................................................13

Annex C (normative) Determination of nickel in combined filtrates by atomic absorption

spectrometry........................................................................................................................................15

Bibliography......................................................................................................................................................18

© ISO 2013 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO DIS/4938
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.

ISO 4938 was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 1, Methods of

determination of chemical composition.

This second/third/... edition cancels and replaces the first/second/... edition (ISO 4938:1988), [clause(s) /

subclause(s) / table(s) / figure(s) / annex(es)] of which [has / have] been technically revised.

iv © ISO 2013 – All rights reserved
---------------------- Page: 4 ----------------------
DRAFT INTERNATIONAL STANDARD ISO DIS/4938
Steel and iron — Determination of nickel content — Gravimetric
or titrimetric method
1 Scope

This International Standard specifies a method for the determination of nickel in steel and iron, either by

gravimetry or by titrimetry.
The method is applicable to nickel contents from 1 % to 30 % (mass fraction).
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 4793, Laboratory sintered (fritted) filters — Porosity grading, classification and designation

ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical

composition.
3 Principle
Dissolution of a test portion with appropriate acids,
Precipitation of the nickel as nickel-diméthylglyoxime.
⎯ Cobalt, if present, is oxidized by potassium hexacyanoferrate(lll);

⎯ Copper, if present with cobalt, preferably is removed by controlled potential electrolysis.

Acid dissolution of the precipitate and filtration of the solution, followed by a second precipitation of the nickel

as nickel diméthylglyoxime.

In the case of the gravimetric determination, weighing of the dried diméthylglyoxime precipitate.

In the case of the titrimetric determination, acid dissolution of the precipitate, addition of excess EDTA.Na

solution and back titration of the excess EDTA.Na by zinc solution using xylenol orange as an indicator.

© ISO 2013 – All rights reserved
---------------------- Page: 5 ----------------------
ISO DIS/4938

In both cases, determination of residual nickel in the filtrate(s) by atomic absorption spectrometry.

4 Reagents

During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only

distilled water grade 2 water as specified in ISO 3696 or water of equivalent purity.

4.1 Sodium hydrogen sulphate (NaHSO )
4.2 Ethanol, 95 % (V/V)
4.3 Acetic acid, glacial, ρ approximately 1,05 g/ml
4.4 Hydrofluoric acid, ρ approximately 1,15 g/ml

WARNING — Hydrofluoric acid is extremely irritating and corrosive to skin and mucous membranes

producing severe skin burns which are slow to heal. In the case of contact with skin, wash well with

water, apply a topical gel containing 2,5 % (mass fraction) calcium gluconate, and seek immediate

medical treatment.
4.5 Nitric acid, ρ approximately 1,40 g/ml
4.6 Perchloric acid, ρ approximately 1,54 g/ml

WARNING —Perchloric acid vapour may cause explosions in the presence of ammonia, nitrous fumes

or organic material in general.
4.7 Sulphuric acid, ρ approximately 1,84 g/ml
4.8 Ammonia solution, ρ approximately 0,90 g/ml
4.9 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted 1 + 1
Add 500 ml of hydrochloric acid (ρ approximately 1,19 g/ml) to 500 ml of water.
4.10 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted 1 + 99
Add 10 ml of hydrochloric acid (ρ approximately 1,19 g/ml) to 990 ml of water.
4.11 Nitric acid, ρ approximately 1,40 g/ml, diluted 2 + 3
Add 200 ml of nitric acid (4.5) to 300 ml of water.
4.12 Perchloric acid, ρ approximately 1,54 g/ml, diluted 1 + 49
Add 10 ml of perchloric acid (4.6) to 490 ml of water.
4.13 Ammonia solution, ρ approximately 0,90 g/ml, diluted 1 + 1
Add 500 ml of ammonia solution (4.8) to 500 ml of water.
© ISO 2013 – All rights reserved
---------------------- Page: 6 ----------------------
ISO DIS/4938
4.14 Ammonia solution, ρ approximately 0,90 g/ml, diluted 1 + 3
Add 100 ml of ammonia solution (4.8) to 300 ml of water.
4.15 Hydrochloric/nitric acids mixture

Mix three volumes of hydrochloric acid (ρ approximately 1,19 g/ml) with one volume of nitric acid (4.5).

Prepare this mixture immediately prior to use.
4.16 Ammonium acetate, 200 g/l solution
4.17 Ammonium citrate buffer solution

Dissolve 500 g of citric acid monohydrate (C H O . H O) in 675 ml of ammonia solution (4.8) and dilute to 1 l

6 8 7 2
with water.
Filter before use.
4.18 Citric acid, 500 g/l solution

Dissolve 500 g of citric acid monohydrate (C H O . H O) in water and dilute to 1 l with water.

6 8 7 2
Filter before use.
4.19 Dimethylglyoxime, 30 g/l solution in alkaline medium

Dissolve 20 g of potassium hydroxide in 400 ml of water, add 30 g of dimethylglyoxime (C H N O ) and stir

4 8 2 2
until dissolution is complete. Dilute to 1 l with water and mix.
Filter before use.
4.20 Dimethylglyoxime, 10 g/l solution in ethanol
Dissolve 10 g of dimethylglyoxime (C H N O ) in 1 000 ml of ethanol (4.2).
4 8 2 2
Filter before use.
4.21 Hydrazine dihydrogen sulphate (N H SO ), 100 g/l solution
2 6 4
4.22 Potassium hexacyanoferrate(lll), K [Fe(CN) ], 100 g/l solution
3 6
This solution is stable for approximately 30 days.

1 ml of this solution corresponds approximately to 0,02 g of cobalt and manganese, respectively.

4.23 Washing water, adjusted to pH 8 with a few drops of ammonia solution (4.13)

4.24 Ethylenediaminetetraacetic acid disodium salt (EDTA.Na ), standard-volumetric solution

4.24.1 Preparation of the solution

Dissolve 6,33 g of ethylenediaminetetraacetic acid disodium salt (C H O N Na . 2H O) in water, transfer the

10 14 8 2 2 2
solution to a 1 000 ml one-mark volumetric flask, dilute to the mark and mix.
© ISO 2013 – All rights reserved
---------------------- Page: 7 ----------------------
ISO DIS/4938
1 ml of this standard solution corresponds approximately to 1 mg of nickel.
4.24.2 Standardization of the solution

Transfer 25,0 ml of the nickel standard solution (4.24.3) to a 250 ml beaker, and add 33 ml of EDTA.Na

solution (4.24.1). Add 15 ml of ammonium acetate solution (4.16) and dilute to about 150 ml with water.

Continue as described in the third paragraph of 7.2.5.

The corresponding concentration c of the EDTA.Na solution (4.24.1), expressed in milligrams of nickel per

millilitre, is given by the equation:
(m1 x 25)+ (m2 x V1)
c =
where

m is the mass, in milligrams, of nickel contained in 1 ml of the nickel standard solution (4.24.3);

m is the mass, in milligrams, of nickel corresponding to 1 ml of the zinc standard solution (4.25);

V is the volume, in millilitres, of the zinc standard solution (4.25) used for the titration;

V is the volume, in millilitres, of the EDTA.Na solution (4.24.1) used for the standardization.

2 2
4.24.3 Nickel standard solution

Weigh, to the nearest 0,1 mg, 1,000 g of nickel [Ni > 99,95 % (m/m)]. Dissolve in 20 ml of nitric acid (4.11).

Boil to remove nitrous fumes, cool, transfer quantitatively to a 1 000 ml one-mark volumetric flask, dilute to the

mark and mix.
1 ml of this standard solution contains 1,0 mg of nickel.
4.25 Zinc, standard solution

Weigh, to the nearest 0,1 mg, 1,1140 g of zinc [purity > 99,9 % (m/m)] and transfer to a 300 ml beaker. If the

zinc metal is oxidized, it should be cleaned with hydrochloric acid (4.9), water and acetone, respectively, and

dried for 5 min at 110 °C before use.

Add about 50 ml of water, 20 ml of hydrochloric acid (4.9) and five drops of bromine-saturated water. Cover

with a watch glass and heat until the metal is completely dissolved. Continue the heating until the colour of the

bromine disappears, cool to room temperature and add 20 ml of acetic acid (4.3). Adjust the pH of the solution

to 6,0 ± 0,2 with ammonia solution (4.14). Transfer quantitatively to a 1 000 ml one-mark volumetric flask,

dilute to the mark and mix.

1 ml of this standard solution corresponds to 1,0 mg of Ni and also approximately to 1 ml of the EDTA.Na

standard volumetric solution (4.24).
4.26 Xylenol orange, 1 g/l solution
5 Apparatus

All volumetric glassware shall be grade A. in accordance with ISO 385, ISO 648 or ISO 1042, as appropriate.

The apparatus consists of ordinary laboratory equipment, and
© ISO 2013 – All rights reserved
---------------------- Page: 8 ----------------------
ISO DIS/4938
5.1 Sintered-glass filter, complying with porosity grade P16 of ISO 4793
5.2 pH-meter

5.3 Apparatus for controlled-potential electrolysis, with a saturated calomel reference electrode

and a platinum electrode
6 Sampling

Carry out sampling in accordance with ISO 14284 or appropriate national standards for iron.

7 Procedure
7.1 Test portion

The test portion shall be selected so that the amount of nickel to be precipitated is within the range 25 mg to

70 mg for the gravimetric determination and 25 mg to 40 mg for the titrimetric determination.

For example, if 3,5 % (mass fraction) nickel content is expected, weigh approximately a 1 g test portion. All

weightings shall be to the nearest 0,1 mg.
7.2 Determination
7.2.1 Preparation of the test solution

Place the test portion (7.1) in a beaker of suitable capacity (e.g. 400 ml for test portions up to 2,5 g and 600 ml

for test portions above 2,5 g). Add 30 ml of hydrochloric-nitric acids mixture (4.15) for test portions up to 2,5 g

and 50 ml for other test portions. Cover the beaker with a watch-glass and heat at 50 °C to 60 °C until reaction

is complete and then add 0,5 ml to 1 ml of hydrofluoric acid (4.4). Add 30 ml of perchloric acid (4.6) for test

portions up to 2,5 g, and 50 ml for other test portions.

Increase the temperature to approximately 180 °C and evaporate the solution until copious white fumes of

perchloric acid are evolved.

Cover the beaker with a dry watch-glass and continue fuming until the chromium, if present, is completely

oxidized (at that stage, the solution gets the orange dichromate colour).

Remove the beaker from the heat and allow to cool. Add 100 ml of water and heat to dissolve the salts. Boil

for about 5 min to eliminate chlorine compounds.

Filter through a rapid filter paper to remove graphite and oxides of silicon, tungsten, niobium and tantalum,

collecting the filtrate in an 800 ml beaker and washing 8 to 10 times with hot perchloric acid (4.12) followed by

two washings with water.
NOTE This solution is a main solution.

Transfer the filter and residue to a platinum crucible. Dry, ash and ignite at a temperature of 900 °C. Treat the

residue with hydrofluoric acid (4.4), evaporate and fuse the residue by carefully heating the crucible with a

small amount of sodium hydrogen sulphate (4.1).
Cool the melt, dissolve it in hot water and add to the main solution.
© ISO 2013 – All rights reserved
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ISO DIS/4938
7.2.2 First nickel precipitation

7.2.2.1 For test portions containing less than 5 mg of copper and less than 5 mg of cobalt

Dilute the test solution prepared in 7.2.1 to approximately 400 ml with water and add 50 ml of citric acid

solution (4.18). Neutralize with ammonia solution (4.13) and re-acidify slightly with hydrochloric acid (4.9).

Heat to 90 °C and directly pour into the solution 10 ml of dimethylglyoxime solution (4.20) for every 10 mg of

nickel present.

Neutralize the solution with ammonia solution (4.13), add 2 ml excess and stir well. St

...

NORME ISO
INTERNATIONALE 4938
Deuxième édition
2016-02-01
Aciers et fontes — Détermination du
nickel — Méthode gravimétrique ou
titrimétrique
Steel and iron — Determination of nickel content — Gravimetric or
titrimetric method
Numéro de référence
ISO 4938:2016(F)
ISO 2016
---------------------- Page: 1 ----------------------
ISO 4938:2016(F)
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© ISO 2016, Publié en Suisse

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ii © ISO 2016 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 4938:2016(F)
Sommaire Page

Avant-propos ..............................................................................................................................................................................................................................iv

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Principe .......................................................................................................................................................................................................................... 1

4 Réactifs ........................................................................................................................................................................................................................... 1

5 Appareillage .............................................................................................................................................................................................................. 4

6 Prélèvement .............................................................................................................................................................................................................. 5

7 Mode opératoire.................................................................................................................................................................................................... 5

7.1 Prise d’essai ............................................................................................................................................................................................... 5

7.2 Détermination ......................................................................................................................................................................................... 5

7.2.1 Préparation de la solution pour essai ............................................................................................................ 5

7.2.2 Première précipitation du nickel ....................................................................................................................... 6

7.2.3 Deuxième précipitation du nickel ..................................................................................................................... 7

7.2.4 Gravimétrie ........................................................................................................................................................................... 7

7.2.5 Titrimétrie ............................................................................................................................................................................. 7

8 Expression des résultats............................................................................................................................................................................... 8

8.1 Méthode de calcul ................................................................................................................................................................................. 8

8.1.1 Gravimétrie ........................................................................................................................................................................... 8

8.1.2 Titrimétrie ............................................................................................................................................................................. 8

8.2 Fidélité ........................................................................................................................................................................................................... 9

9 Rapport d’essai ....................................................................................................................................................................................................... 9

Annexe A (informative) Informations supplémentaires sur l’essai interlaboratoires ..................................11

Annexe B (informative) Représentation graphique des données de fidélité ..........................................................13

Annexe C (normative) Détermination du nickel dans les filtrats combinés par

spectrométrie d’absorption atomique .......................................................................................................................................15

Bibliographie ...........................................................................................................................................................................................................................18

© ISO 2016 – Tous droits réservés iii
---------------------- Page: 3 ----------------------
ISO 4938:2016(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www.

iso.org/directives).

L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www.iso.org/brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer

un engagement.

Pour une explication de la signification des termes et expressions spécifiques de l’ISO liés à

l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion de l’ISO aux principes

de l’OMC concernant les obstacles techniques au commerce (OTC), voir le lien suivant: Avant-propos —

Informations supplémentaires.

Le comité chargé de l’élaboration du présent document est l’ISO/TC 17, Acier, sous-comité SC 1, Méthodes

de détermination de la composition chimique.

Cette deuxième édition annule et remplace la première édition (ISO 4938:1988) qui a été révisée

techniquement.
iv © ISO 2016 – Tous droits réservés
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NORME INTERNATIONALE ISO 4938:2016(F)
Aciers et fontes — Détermination du nickel — Méthode
gravimétrique ou titrimétrique
1 Domaine d’application

La présente Norme internationale spécifie une méthode gravimétrique ou titrimétrique de

détermination du nickel dans les aciers et les fontes.

La méthode est applicable aux teneurs en nickel comprises entre 1 % et 30 % (fraction massique).

2 Références normatives

Les documents de référence suivants sont indispensables pour l’application du présent document. Pour

les références datées, seule l’édition citée s’applique. Pour les références non datées, la dernière édition

du document de référence s’applique (y compris les éventuels amendements).
ISO 648, Verrerie de laboratoire — Pipettes à un volume
ISO 1042, Verrerie de laboratoire — Fioles jaugées à un trait

ISO 3696, Eau pour laboratoire à usage analytique — Spécification et méthodes d’essai

ISO 4793, Filtres frittés de laboratoire — Échelle de porosité — Classification et désignation

ISO 14284, Fontes et aciers — Prélèvement et préparation des échantillons pour la détermination de la

composition chimique
3 Principe
Mise en solution d’une prise d’essai par des acides appropriés.
Précipitation du nickel sous la forme de nickel-diméthylglyoxime.

— Le cobalt éventuellement présent est oxydé par l’hexacyanoferrate (III) de potassium.

— Le cuivre, éventuellement présent avec le cobalt, doit de préférence être éliminé par électrolyse

sous potentiel contrôlé.

Dissolution acide du précipité et filtration de la solution suivie d’une seconde précipitation du nickel

sous la forme de nickel-diméthylglyoxime.

Dans le cas de la gravimétrie, pesée du précipité de nickel-diméthylglyoxime séché.

Dans le cas de la titrimétrie, dissolution acide du précipité, ajout d’une solution de d’EDTA.Na en excès

et titrage en retour de l’excès d’EDTA.Na par une solution étalon de zinc, en présence de xylénol orange

comme indicateur.

Dans les deux cas, détermination du nickel résiduel dans le(s) filtrat(s) par spectrométrie d’absorption

atomique (voir Annexe C).
4 Réactifs

Au cours de l’analyse, sauf indication contraire, utiliser uniquement des réactifs de qualité analytique

reconnue et de l’eau distillée de grade 2, comme spécifié par l’ISO 3696, ou de pureté équivalente.

© ISO 2016 – Tous droits réservés 1
---------------------- Page: 5 ----------------------
ISO 4938:2016(F)
4.1 Hydrogénosulfate de sodium (NaHSO ).
4.2 Ethanol, 95 % (fraction volumique).
4.3 Acide acétique cristallisé, ρ 1,05 g/ml environ.
4.4 Acide fluorhydrique, ρ 1,15 g/ml environ.

AVERTISSEMENT — L’acide fluorhydrique est extrêmement irritant et corrosif pour la peau et

les muqueuses et provoque de sévères brûlures de la peau, longues à guérir. En cas de contact

avec la peau, bien nettoyer avec de l’eau, appliquer un gel topique contenant 2,5 % (fraction en

masse) de gluconate de calcium et consulter immédiatement un médecin.
4.5 Acide nitrique, ρ 1,40 g/ml environ.
4.6 Acide perchlorique, ρ 1,54 g/ml environ.

AVERTISSEMENT — Les vapeurs d’acide perchlorique peuvent produire des explosions en

présence d’ammoniac, de vapeurs nitreuses ou de matières organiques en général.
4.7 Acide sulfurique, ρ 1,84 g/ml environ.
4.8 Ammoniaque, solution ρ 0,90 g/ml environ.
4.9 Acide chlorhydrique, ρ 1,19 g/ml environ, dilué 1 + 1.
Ajouter 500 ml d’acide chlorhydrique (ρ environ 1,19 g/ml) à 500 ml d’eau.
4.10 Acide chlorhydrique, ρ 1,19 g/ml environ, dilué 1 + 99.
Ajouter 10 ml d’acide chlorhydrique (ρ environ 1,19 g/ml) à 990 ml d’eau.
4.11 Acide nitrique, ρ 1,40 g/ml environ, dilué 2 + 3.
Ajouter 200 ml d’acide nitrique (4.5) à 300 ml d’eau.
4.12 Acide perchlorique, ρ 1,54 g/ml environ, dilué 1 + 49.
Ajouter 10 ml d’acide perchlorique (4.6) à 490 ml d’eau.
4.13 Ammoniaque, ρ 0,90 g/ml environ, diluée 1 + 1.
Ajouter 500 ml d’ammoniac (4.8) à 500 ml d’eau.
4.14 Ammoniaque, ρ 0,90 g/ml environ, diluée 1 + 3.
Ajouter 100 ml d’ammoniac (4.8) à 300 ml d’eau.
4.15 Mélange d’acides chlorhydrique et nitrique.

Mélanger trois volumes d’acide chlorhydrique (ρ 1,19 g/ml environ) et un volume d’acide nitrique (4.5).

Cette solution doit être préparée juste avant l’emploi.
4.16 Acétate d’ammonium, solution à 200 g/l.
2 © ISO 2016 – Tous droits réservés
---------------------- Page: 6 ----------------------
ISO 4938:2016(F)
4.17 Solution tampon de citrate d’ammonium.

Dissoudre 500 g d’acide citrique monohydraté (C H O ·H O) dans 675 ml d’ammoniaque (4.8) et diluer

6 8 7 2
à 1 l avec de l’eau.
Filtrer avant l’emploi.
4.18 Acide citrique, solution à 500 g/l.

Dissoudre 500 g d’acide citrique monohydraté (C H O ·H O) dans de l’eau et diluer à 1 l.

6 8 7 2
Filtrer avant l’emploi.
4.19 Diméthylglyoxime, solution à 30 g/l en milieu alcalin.

Dissoudre 20 g d’hydroxyde de potassium dans 400 ml d’eau, ajouter 30 g de diméthylglyoxime

(C H N O ) et agiter jusqu’à dissolution complète. Diluer à 1 l avec de l’eau et homogénéiser.

4 8 2 2
Filtrer avant l’emploi.
4.20 Diméthylglyoxime, solution à 10 g/l en milieu éthanolique.
Dissoudre 10 g de diméthylglyoxime (C H N O ) dans 1 000 ml d’éthanol (4.2).
4 8 2 2
Filtrer avant l’emploi.
4.21 Dihydrogeno sulfate d’hydrazine (N H SO ), solution à 100 g/l.
2 6 4
4.22 Hexacyanoferrate (III) de potassium, K [Fe(CN) ], solution à 100 g/l.
3 6
Cette solution est stable pendant 30 jours environ.

1 ml correspond approximativement à environ 0,02 g de cobalt et manganèse, respectivement.

4.23 Eau de rinçage, ajustée à pH 8 à l’aide de quelques gouttes d’ammoniaque (4.13).

4.24 Ethylène-diamine-tétraacétate de sodium (EDTA.Na ), solution étalon.
4.24.1 Préparation de la solution

Dissoudre 6,33 g d’éthylène-diamine-tétraacétate de sodium (C H O N Na ·2H O) dans de l’eau,

10 14 8 2 2 2

transvaser dans une fiole jaugée de 1 000 ml, compléter au volume avec de l’eau et homogénéiser.

1 ml de cette solution étalon correspond à environ 1 mg de nickel.
4.24.2 Étalonnage de la solution

Introduire 25,0 ml de la solution étalon de nickel (4.24.3) dans un bécher de 250 ml et ajouter 33 ml de

solution d’EDTA.Na (4.24.1). Ajouter 15 ml de solution d’acétate d’ammonium (4.16) et diluer à environ

150 ml avec de l’eau. Continuer comme indiqué au troisième alinéa en 7.2.5.
© ISO 2016 – Tous droits réservés 3
---------------------- Page: 7 ----------------------
ISO 4938:2016(F)

La concentration correspondante, c, de solution étalon d’EDTA.Na (4.24.1) exprimée en milligrammes

de nickel par millilitre, est donnée par la Formule (1):
mm×25 +×V
() ()
12 1
c = (1)

m est la masse de nickel contenu dans 1 ml de la solution étalon de nickel (4.24.3), en milligrammes;

m est la masse de nickel correspondant à 1 ml de la solution étalon de zinc (4.25), en milligrammes;

V est le volume de solution étalon de zinc (4.25) utilisé pour le titrage, en millilitres;

V est le volume de solution étalon d’EDTA.Na (4.24.1) utilisé pour l’étalonnage, en millilitres.

2 2
4.24.3 Préparation de la solution étalon de nickel

Peser à 0,1 mg près, 1,000 g de nickel [Ni > 99,95 % (fraction massique)]. Mettre en solution par

20 ml d’acide nitrique (4.11). Faire bouillir pour éliminer les vapeurs nitreuses, refroidir, transvaser

quantitativement dans une fiole jaugée de 1 000 ml, compléter au volume avec de l’eau et homogénéiser.

1 ml de cette solution de référence contient 1,0 mg de Ni.
4.25 Zinc, solution étalon.

Peser à 0,1 mg près, 1,114 0 g de zinc [pureté > 99,9 % (fraction massique)], et les introduire dans un

bécher de 300 ml. Si le zinc est oxydé, il devrait être nettoyé avec de l’acide chlorhydrique (4.9), de l’eau

et de l’acétone, et séché pendant 5 min à 110 °C.

Ajouter environ 50 ml d’eau, 20 ml d’acide chlorhydrique (4.9) et 5 gouttes d’eau de brome saturée.

Couvrir d’un verre de montre et chauffer jusqu’à mise en solution complète du métal. Poursuivre le

chauffage jusqu’à ce que la coloration du brome disparaisse, refroidir à température ambiante et ajouter

20 ml d’acide acétique cristallisé (4.3). Ajuster le pH de la solution à 6,0 ± 0,2 avec de l’ammoniaque

(4.14). Transvaser quantitativement dans une fiole jaugée de 1 000 ml, compléter au volume avec de

l’eau et homogénéiser.

1 ml de cette solution étalon correspond à 1,0 mg de Ni et aussi approximativement à 1 ml de la solution

étalon d’EDTA.Na (4.24).
4.26 Xylénol orange, solution à 1 g/l.

Pulvériser 0,1 g de xylénol orange (C H N O SNa ) avec un peu d’eau pour former une pâte. Diluer à

31 28 2 13 4

100 ml avec de l’eau. Filtrer et conserver la solution dans un récipient fermé en verre ambré.

Cette solution est stable pendant une semaine.
5 Appareillage

Toute la verrerie jaugée doit être de classe A, conformément à l’ISO 648 ou à l’ISO 1042, selon le cas;

Outre du matériel courant de laboratoire, on doit utiliser ce qui suit.
5.1 Filtres en verre frité, de porosité P16, conformément à l’ISO 4793.
5.2 pH-mètre.
4 © ISO 2016 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 4938:2016(F)

5.3 Appareillage d’électrolyse à potentiel contrôlé, avec électrode de référence au calomel saturé et

électrode de platine.
6 Prélèvement

Effectuer le prélèvement conformément aux spécifications de l’ISO 14284 ou des normes nationales

appropriées relatives aux aciers et fontes.
7 Mode opératoire
7.1 Prise d’essai

La prise d’essai doit être choisie de sorte que la quantité de nickel à précipiter se situe entre 25 mg et

70 mg pour la gravimétrie, et entre 25 mg et 40 mg pour la titrimétrie.

Par exemple, si la teneur probable en nickel est de 3,5 % (fraction massique), peser environ 1 g de prise

d’essai. Toutes les pesées doivent se faire à 0,1 mg près.
7.2 Détermination
7.2.1 Préparation de la solution pour essai

Introduire la prise d’essai (7.1) dans un bécher de volume convenable (par exemple, 400 ml pour des

prises d’essai inférieures ou égales à 2,5 g, et 600 ml pour des prises d’essai supérieures à 2,5 g). Ajouter

30 ml du mélange d’acides chlorhydrique et nitrique (4.15) pour les prises d’essai inférieures ou égales

à 2,5 g, et 50 ml pour les autres prises d’essai. Couvrir le bécher d’un verre de montre et chauffer entre

50 °C et 60 °C jusqu’à ce que la réaction soit terminée, puis ajouter 0,5 ml à 1 ml d’acide fluorhydrique

(4.4). Ajouter ensuite 30 ml d’acide perchlorique (4.6) pour les prises d’essai inférieures ou égales à

2,5 g et 50 ml pour les autres prises d’essai.

Elever la température jusqu’à environ 180 °C et évaporer la solution jusqu’à dégagement d’intenses

fumées blanches d’acide perchlorique.

Couvrir le bécher d’un verre de montre sec et poursuivre le chauffage à fumées jusqu’à oxydation

complète du chrome, s’il est présent (à ce stade, la solution prend la couleur orange du dichromate).

Enlever le bécher de la source de chaleur et laisser refroidir. Ajouter 100 ml d’eau et chauffer pour

dissoudre les sels. Faire bouillir pendant 5 min environ pour éliminer les composés chlorés.

Filtrer sur un filtre à filtration rapide pour éliminer le graphite et les oxydes de silicium, de tungstène,

de niobium et de tantale. Recueillir le filtrat dans un bécher de 800 ml et rincer huit à dix fois avec de

l’acide perchlorique (4.12) chaud, puis deux fois avec de l’eau.
NOTE Cette solution est la solution principale.

Introduire le filtre et le résidu dans un creuset de platine. Sécher, incinérer puis calciner à une

température de 900 °C. Traiter le résidu avec de l’acide fluorhydrique (4.4), évaporer et fondre le résidu

avec une petite quantité d’hydrogenosulfate de sodium (4.1), en chauffant modérément le creuset.

Laisser refroidir le creuset, reprendre les produits de fusion par de l’eau chaude et joindre à la

solution principale.
© ISO 2016 – Tous droits réservés 5
---------------------- Page: 9 ----------------------
ISO 4938:2016(F)
7.2.2 Première précipitation du nickel

7.2.2.1 Ce qui suit s’applique aux prises d’essai contenant moins de 5 mg de cuivre

...

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