ISO 4941

Steel and iron — Determination of molybdenum content — Thiocyanate spectrophotometric method

Cancels and replaces the first edition (1978). Specifies a thiocyanate spectrophotometric method for the determination of the molybdenum content in steel and iron. Applicable to molybdenum contents between 0,005 % (m/m) and 0,125 % (m/m). Vanadium and tungsten interfere with the measurement if, because of their contents, the V/Mo ratio is greater than 16 or the W/Mo ratio is greater than 8.

Aciers et fontes — Détermination des teneurs en molybdène — Méthode spectrophotométrique au thiocyanate

General Information

• Status: Not Published
• ICS: 77.080.01 - Ferrous metals in general
• Technical Committee: ISO/TC 17/SC 1 - Methods of determination of chemical composition
• Drafting Committee: ISO/TC 17/SC 1 - Methods of determination of chemical composition
• Current Stage: 6000 - International Standard under publication
• Completion Date: 05-Jul-2024

Relations

• Revises: ISO 4941:1994 - Steel and iron — Determination of molybdenum content — Thiocyanate spectrophotometric method
• Effective Date: 28-Jan-2023

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 4941
ISO/TC 17/SC 1
Steel and iron — Determination
Secretariat: JISC
of molybdenum content —
Voting begins on:
Thiocyanate spectrophotometric
2024-05-09
method
Voting terminates on:
2024-07-04
Aciers et fontes — Dosage des teneurs en molybdène — Méthode
spectrophotométrique au thiocyanate
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 4941:2024(en) © ISO 2024

FINAL DRAFT
ISO/FDIS 4941:2024(en)
International
Standard
ISO/FDIS 4941
ISO/TC 17/SC 1
Steel and iron — Determination of
Secretariat: JISC
molybdenum content — Thiocyanate
Voting begins on:
spectrophotometric method
Aciers et fontes — Dosage des teneurs en molybdène — Méthode
Voting terminates on:
spectrophotométrique au thiocyanate
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 SUPPOR TING DOCUMENTATION.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 4941:2024(en) © ISO 2024

ii
ISO/FDIS 4941:2024(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 3
7 Sampling and preparation of the test samples . 3
8 Procedure . 3
8.1 Test portion .4
8.2 Determination .4
8.2.1 Preparation of the test solution .4
8.2.2 Preparation of the compensating solution .4
8.2.3 Formation and extraction of the coloured complex .4
8.2.4 Spectrophotometric measurements .5
8.3 Establishment of the calibration curve .5
8.3.1 Preparation of the calibration solutions, related to spectrophotometric
measurements performed using cells with an optical path length of 10 mm .5
8.3.2 Spectrophotometric measurements .5
8.3.3 Plotting the calibration curve .6
9 Expression of results . 6
9.1 Method of calculation .6
9.2 Precision . . .7
10 Test report . 7
Annex A (informative) Additional information on the international interlaboratory test . 8
Annex B (informative) Graphical representation of precision data .10
Bibliography .11

iii
ISO/FDIS 4941:2024(en)
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 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)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
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 17, Steel, Subcommittee SC 1, Methods of
determination of chemical composition.
This third edition cancels and replaces the second edition (ISO 4941:1994), which has been technically
revised.
The main changes are as follows:
— the normative references have been revised;
— the precision data has been updated.
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
FINAL DRAFT International Standard ISO/FDIS 4941:2024(en)
Steel and iron — Determination of molybdenum content —
Thiocyanate spectrophotometric method
1 Scope
This document specifies a thiocyanate spectrophotometric method for the determination of the molybdenum
contents in steel and iron. The method is applicable to molybdenum mass fractions between 0,005 % and
0,125 %.
Vanadium and tungsten interfere with the measurement if, because of their contents, the V/Mo ratio is
greater than 16 or the W/Mo ratio is greater than 8.
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 4800, Laboratory glassware — Separating funnels and dropping funnels
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical composition
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 https:// www .electropedia .org/
4 Principle
Dissolution of a test portion in an appropriate mixture of acids and decomposition of the carbides by
oxidation.
Quantitative formation of a coloured complex of molybdenum, in the presence of thiocyanate, iron(II) and/
or copper(II) ions and extraction of this compound using butyl acetate.
Spectrophotometric measurement of the coloured complex at a wavelength of about 470 nm.

ISO/FDIS 4941:2024(en)
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and grade 2
water as specified in ISO 3696.
5.1 Pure iron, in flake or powder form, with a molybdenum content less than 0,000 5 % (mass fraction)
and free from tungsten and vanadium.
5.2 Butyl acetate.
5.3 Nitric acid, ρ approximately 1,40 g/ml.
5.4 Hydrochloric acid, ρ approximately 1,19 g/ml.
5.5 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted (3 + 1).
5.6 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted (1 + 1).
5.7 Acid mixture I.
Add 2 volumes of hydrochloric acid (5.4) to 1 volume of nitric acid (5.3) and mix well. Prepare this mixture
immediately before use.
5.8 Acid mixture II.
Add 150 ml of orthophosphoric acid (ρ approximately 1,70 g/ml) to 300 ml of water, and add 360 ml of
perchloric acid (ρ approximately 1,67 g/ml) to this diluted acid (see NOTE). Transfer the solution into a
1 000 ml, one-mark volumetric flask, dilute to the mark with water and mix.
NOTE In the preparation of this acid mixture, 360 ml of perchloric acid (ρ approximately 1,67 g/ml) can be
replaced by 150 ml of sulfuric acid (ρ approximately 1,84 g/ml).
5.9 L(+)- ascorbic acid solution, 100 g/l.
Prepare this solution just before use.
5.10 Ammonium thiocyanate solution, 320 g/l.
Store this solution away from light.
5.11 Copper(II), solution corresponding to 70 mg of Cu(II) per litre in a hydrochloric acid medium.
Dissolve 0,188 g of copper(II) chloride di-hydrate (CuCl .2H O) or 0,275 g of copper(II) sulfate penta-
2 2
hydrate (CuSO .5H O) into 125 ml of hydrochloric acid (5.4). Transfer the solution into a 1 000 ml one-mark
4 2
volumetric flask, dilute to the mark with water and mix.
5.12 Tin(II) copper(II) chloride, solution in a hydrochloric acid medium.
Dissolve 80 g of tin(II) chloride di-hydrate (SnCl .2H O) in 155 ml of hydrochloric acid (5.4). Add 100 ml
2 2
of copper(II) solution (5.11). Transfer the solution into a 1 000 ml one-mark volumetric flask, dilute to the
mark with water and mix.
Prepare this solution just before use.
...

2024-04-14
Style Definition
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ISO/DIS FDIS 4941:2023(E)
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ISO /TC 17/SC 1/WG 1
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Steel and iron — Determination of molybdenum content —
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Thiocyanate spectrophotometric method
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Aciers et fontes — Dosage des teneurs en molybdène — Méthode spectrophotométrique au thiocyanate
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
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or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
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CP 401 • Ch. de Blandonnet 8
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ii © ISO 2023 2024 – All rights reserved
ii
ISO/DIS FDIS 4941:2023(E2024(en) Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: 11 pt, Bold, Font color: Auto
Contents
Formatted: Font: 11 pt, Bold
Formatted: HeaderCentered, Left, Space After: 0 pt,
Foreword . v
Line spacing: single
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 3
7 Sampling and preparation of the test samples . 3
8 Procedure . 3
8.1 Test portion . 4
8.2 Determination . 4
8.2.1 Preparation of the test solution . 4
8.2.2 Preparation of the compensating solution . 4
8.2.3 Formation and extraction of the coloured complex . 4
8.2.4 Spectrophotometric measurements . 5
8.3 Establishment of the calibration curve . 5
8.3.1 Preparation of the calibration solutions, related to spectrophotometric measurements
performed using cells with an optical path length of 10 mm . 5
8.3.2 Spectrophotometric measurements . 6
8.3.3 Plotting the calibration curve . 6
9 Expression of results . 6
9.1 Method of calculation . 6
9.2 Precision . 7
10 Test report . 8
Annex A (informative) Additional information on the international interlaboratory test . 9
Annex B (informative) Graphical representation of precision data . 11
Bibliography . 13

Foreword . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagent . 2
6 Apparatus . 3
7 Sampling and preparation of the test samples . 4
8 Procedure . 4
9 Expression of results . 7
Formatted: Font: 11 pt
10 Test report . 9
Formatted: FooterPageRomanNumber, Line spacing:
Annex A (informative) Additional information on international inter-laboratory test . 10
single
iii
ISO/DIS FDIS 4941:2023(E2024(en) Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: 11 pt, Bold, Font color: Auto
Annex B (informative) Graphical representation of precision data . 12
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Bibliography . 13
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spacing: single
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single
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iv © ISO 2023 2024 – All rights reserved
iv
ISO/DIS FDIS 4941:2023(E2024(en) Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: HeaderCentered, Left, Space After: 0 pt,
Line spacing: single
Foreword
Formatted: Font: 11 pt, Bold, Font color: Auto
Formatted: Font: 11 pt, Bold, Font color: Auto
ISO (the International Organization for Standardization) is a worldwide federation of national standards
Formatted: Font: 11 pt, Bold
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 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) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
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.htmlwww.iso.org/iso/foreword.html.
Formatted: English (United Kingdom)
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 1, Methods of
determination of chemical composition.
This third edition cancels and replaces the second edition (ISO 4941:1994), which has been technically
revised.
The main changes are as follows:
— — the normative references have been revised;
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
— — the precision data has been updated.
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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.
Field Code Changed
Formatted: Font: 11 pt
Formatted: FooterPageRomanNumber, Line spacing:
single
v
ISO/FDIS 4941:2024(en)
Formatted: HeaderCentered
Formatted: Font: Bold
Formatted: Main Title 1, Adjust space between Latin
Steel and iron — Determination of molybdenum content —
and Asian text, Adjust space between Asian text and
Thiocyanate spectrophotometric method
numbers
1 Scope
This document specifies a thiocyanate spectrophotometric method for the determination of the molybdenum
contents in steel and iron. The method is applicable to molybdenum mass fractions between 0,005 % and
0,125 %.
Vanadium and tungsten interfere with the measurement if, because of their contents, the V/Mo ratio is greater
than 16 or the W/Mo ratio is greater than 8.
Formatted: Default Paragraph Font
2 Normative references
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
The following documents are referred to in the text in such a way that some or all of their content constitutes
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
requirements of this document. For dated references, only the edition cited applies. For undated references,
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
the latest edition of the referenced document (including any amendments) applies.
Formatted: Default Paragraph Font
ISO 385, Laboratory glassware — Burettes
Formatted: Default Paragraph Font
Formatted: Default Paragraph Font
ISO 648, Laboratory glassware — Single-volume pipettes
Formatted: Default Paragraph Font
ISO 1042, Laboratory glassware — One-mark volumetric flasks
Formatted: Default Paragraph Font
ISO 3696, Water for analytical laboratory use — Specification and test methods
Formatted: Default Paragraph Font
Formatted: Default Paragraph Font
ISO 4800, Laboratory glassware — Separating funnels and dropping funnels
Formatted: Default Paragraph Font
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical
Formatted: Default Paragraph Font
com
...