Steels and irons — Determination of vanadium content — N-BPHA spectrophotometric method

ISO 4942:2016 specifies an N-benzoylphenylhydroxylamine (N-BPHA) spectrophotometric method for the determination of vanadium in steels and cast irons. It is applicable to vanadium contents between 0,005 % and 0,50 % (mass fraction).

Aciers et fontes — Détermination de la teneur en vanadium — Méthode spectrophotométrique au N-BPHA

General Information

Status
Published
Publication Date
22-Jun-2016
Current Stage
9093 - International Standard confirmed
Start Date
03-Sep-2021
Completion Date
03-Sep-2021
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ISO 4942:2016 - Steels and irons -- Determination of vanadium content -- N-BPHA spectrophotometric method
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INTERNATIONAL ISO
STANDARD 4942
Second edition
2016-07-01
Steels and irons — Determination
of vanadium content — N-BPHA
spectrophotometric method
Aciers et fontes — Détermination de la teneur en vanadium —
Méthode spectrophotométrique au N-BPHA
Reference number
ISO 4942:2016(E)
ISO 2016
---------------------- Page: 1 ----------------------
ISO 4942:2016(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.
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ii © ISO 2016 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4942:2016(E)
Contents Page

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

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Reagents ........................................................................................................................................................................................................................ 1

6 Apparatus ..................................................................................................................................................................................................................... 3

7 Sampling ........................................................................................................................................................................................................................ 3

8 Procedure..................................................................................................................................................................................................................... 3

8.1 Test portion ................................................................................................................................................................................................ 3

8.2 Blank test ..................................................................................................................................................................................................... 3

8.3 Determination ......................................................................................................................................................................................... 4

8.3.1 Preparation of the test solution .......................................................................................................................... 4

8.3.2 Oxidation of vanadium .................. ......................................................................................................................... ..... 4

8.3.3 Colour development and extraction ................................................................................................................ 4

8.3.4 Spectrophotometric measurements ............................................................................................................... 4

8.4 Establishment of the calibration curve .............................................................................................................................. 5

8.4.1 Preparation of the calibration solutions ...................................................................................................... 5

8.4.2 Spectrophotometric measurements ............................................................................................................... 5

8.4.3 Plotting of the calibration curve ......................................................................................................................... 5

9 Expression of results ........................................................................................................................................................................................ 5

9.1 Method of calculation ........................................................................................................................................................................ 5

9.2 Precision ....................................................................................................................................................................................................... 6

10 Special cases .............................................................................................................................................................................................................. 7

11 Test report ................................................................................................................................................................................................................... 7

Annex A (informative) Additional information on the international interlaboratory test..........................8

Annex B (informative) Graphical representation of precision data .................................................................................... 9

Bibliography .............................................................................................................................................................................................................................10

© ISO 2016 – All rights reserved iii
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ISO 4942:2016(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 World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.

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 4942:1988), which has been technically

revised.
iv © ISO 2016 – All rights reserved
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INTERNATIONAL STANDARD ISO 4942:2016(E)
Steels and irons — Determination of vanadium content —
N-BPHA spectrophotometric method
1 Scope

This document specifies an N-benzoylphenylhydroxylamine (N-BPHA) spectrophotometric method for

the determination of vanadium in steels and cast irons.

This document is applicable to vanadium contents between 0,005 % and 0,50 % (mass fraction).

2 Normative references

The following documents are referred to in 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 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 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:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
Dissolution of a test portion with appropriate acids.

Addition of orthophosphoric acid to an aliquot of the sample solution to prevent the interference of iron,

and addition of potassium permanganate to oxidize vanadium to the pentavalent state.

Selective reduction of excess permanganate by sodium nitrite, in the presence of urea and treatment

with N-BPHA and hydrochloric acid to form a complex, followed by extraction of the complex with

trichloromethane.
Spectrophotometric measurement of the absorbance at approximately 535 nm.
5 Reagents

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

grade 2 water as specified in ISO 3696 or water of equivalent purity.
© ISO 2016 – All rights reserved 1
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ISO 4942:2016(E)
5.1 Hydrochloric acid, ρ approximately 1,19 g/ml.
5.2 Hydrochloric acid, ρ approximately 1,19 g/ml, diluted 4 + 1.
Add 400 ml of hydrochloric acid (5.1) to 100 ml of water.
5.3 Nitric acid, ρ approximately 1,40 g/ml.
5.4 Perchloric acid, ρ approximately 1,67 g/ml.

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

fumes or organic material in general.
5.5 Orthophosphoric acid, ρ approximately 1,71 g/ml.
5.6 Orthophosphoric acid, ρ approximately 1,71 g/ml, diluted 1 + 1.
Add 250 ml of orthophosphoric acid (5.5) to 250 ml of water.
5.7 Hydrochloric/nitric acids mixture, 3 + 1.
Mix 300 ml of hydrochloric acid (5.1) with 100 ml of nitric acid (5.3).
Prepare this mixture immediately prior to use.
5.8 Hydrogen peroxide, 300 g/l solution.
5.9 Sodium nitrite, 3 g/l solution.
5.10 Urea, 250 g/l solution.
5.11 Sodium tripolyphosphate (Na P O ), 100 g/l solution.
5 3 10
5.12 Potassium permanganate, 3 g/l solution.
5.13 Trichloromethane (chloroform).

5.14 N-benzoylphenylhydroxylamine [C H CON(OH)C H ], 2,5 g/l solution in trichloromethane.

6 5 6 5
Dissolve 0,25 g of N-BPHA in 100 ml of trichloromethane (5.13).

This solution shall be stored in a brown bottle. Otherwise, it shall be freshly prepared.

5.15 Iron, 10 g/l solution.

Weigh, to the nearest 1 mg, 5,0 g of pure iron (free from vanadium or with a vanadium content as low as

possible and exactly known). Transfer into a 500 ml beaker, cover with a watch-glass and add 100 ml of

the hydrochloric/nitric acids mixture (5.7).
After effervescence has ceased, heat gently to complete the dissolution.

Add 100 ml of perchloric acid (5.4) and raise the temperature until white perchloric acid fumes appear

and then reflux in the beaker. Continue
...

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