1、BS ISO 4942:2016Steels and irons Determination of vanadiumcontent N-BPHAspectrophotometric methodBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 4942:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 4942:2016.It super
2、sedes BS 6200-3.34.2:1989 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee ISE/102, Methods of Chemical Analysis for Iron and Steel.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not
3、 purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 81537 9ICS 77.080.01Compliance with a British Standard cannot confer immunity fromlegal obliga
4、tions.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 4942:2016 ISO 2016Steels and irons Determination of vanadium content N-BPHA spectrophotometric
5、methodAciers et fontes Dtermination de la teneur en vanadium Mthode spectrophotomtrique au N-BPHAINTERNATIONAL STANDARDISO4942Second edition2016-07-01Reference numberISO 4942:2016(E)BS ISO 4942:2016ISO 4942:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Swi
6、tzerlandAll 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 r
7、equested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 4942:2016ISO 4942:2016(E)Foreword iv1 Scope .
8、 12 Normative references 13 Terms and definitions . 14 Principle 15 Reagents 16 Apparatus . 37 Sampling 38 Procedure. 38.1 Test portion 38.2 Blank test . 38.3 Determination . 48.3.1 Preparation of the test solution 48.3.2 Oxidation of vanadium 48.3.3 Colour development and extraction 48.3.4 Spectrop
9、hotometric measurements . 48.4 Establishment of the calibration curve 58.4.1 Preparation of the calibration solutions 58.4.2 Spectrophotometric measurements . 58.4.3 Plotting of the calibration curve . 59 Expression of results 59.1 Method of calculation 59.2 Precision . 610 Special cases 711 Test re
10、port . 7Annex A (informative) Additional information on the international interlaboratory test 8Annex B (informative) Graphical representation of precision data 9Bibliography .10 ISO 2016 All rights reserved iiiContents PageBS ISO 4942:2016ISO 4942:2016(E)ForewordISO (the International Organization
11、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 t
12、he 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 proc
13、edures 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 editori
14、al 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
15、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 explanat
16、ion on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs 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 responsi
17、ble 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 reservedBS ISO 4942:2016INTERNATIONAL STANDARD ISO 4942
18、:2016(E)Steels and irons Determination of vanadium content N-BPHA spectrophotometric method1 ScopeThis 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 bet
19、ween 0,005 % and 0,50 % (mass fraction).2 Normative referencesThe 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
20、 the referenced document (including any amendments) applies.ISO 648, Laboratory glassware Single-volume pipettesISO 1042, Laboratory glassware One-mark volumetric flasksISO 3696, Water for analytical laboratory use Specification and test methodsISO 14284, Steel and iron Sampling and preparation of s
21、amples for the determination of chemical composition3 Terms and definitionsNo 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 b
22、rowsing platform: available at http:/www.iso.org/obp4 PrincipleDissolution 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
23、 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 Reage
24、ntsDuring 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 1BS ISO 4942:2016ISO 4942:2016(E)5.1 Hydrochloric acid, approximately 1,19 g/ml.5.2 Hydrochloric a
25、cid, 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, approximately 1,40 g/ml.5.4 Perchloric acid, approximately 1,67 g/ml.WARNING Perchloric acid vapour may cause explosions in the presence of ammonia, nitrous fumes or organic material
26、 in general.5.5 Orthophosphoric acid, approximately 1,71 g/ml.5.6 Orthophosphoric acid, 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.
27、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 (Na5P3O10), 100 g/l solution.5.12 Potassium permanganate, 3 g/l solution.5.13 Trichloromethane (chloroform).5.14 N-benz
28、oylphenylhydroxylamine C6H5CON(OH)C6H5, 2,5 g/l solution in trichloromethane.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 ir
29、on (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 perchlo
30、ric acid (5.4) and raise the temperature until white perchloric acid fumes appear and then reflux in the beaker. Continue fuming for about 3 min.Cool, add 100 ml of hot water and shake to dissolve salts. Add a few drops of hydrogen peroxide (5.8), heat gradually to boiling and maintain at the boil f
31、or about 2 min.2 ISO 2016 All rights reservedBS ISO 4942:2016ISO 4942:2016(E)Cool and transfer into a 500 ml one-mark volumetric flask, dilute to the mark with water and mix.5.16 Vanadium standard solution, 1,0 g/l.Dry several grams of ammonium metavanadate (NH4VO3) in an oven at 100 C to 105 C for
32、at least 1 h and cool to room temperature in a desiccator.A drying temperature over 110 C will cause the decomposition of ammonium metavanadate. Maintain the drying temperature exactly as specified.Weigh, to the nearest 1 mg, 2,296 g of the dried product, transfer into a 600 ml beaker, add 400 ml of
33、 hot water and heat gently until the product is completely dissolved.Cool, transfer into 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 vanadium.5.17 Vanadium standard solution, 50 mg/l.Transfer 5,0 ml of the vanadium sta
34、ndard solution (5.16) into a 100 ml one-mark volumetric flask, dilute to the mark with water and mix.1 ml of this standard solution contains 50 g of vanadium.6 ApparatusAll volumetric glassware shall be grade A, in accordance with ISO 648 or ISO 1042, as appropriate.Ordinary laboratory equipment and
35、 the following.6.1 Spectrophotometer, equipped to measure absorbance at a wavelength of 535 nm, with cells of 1 cm optical path length.7 SamplingCarry out sampling in accordance with ISO 14284 or appropriate national standards for steels and irons.8 Procedure8.1 Test portionWeigh, to the nearest 1 m
36、g, a test portion of the sample according to Table 1.Table 1 Test portionExpected vanadium content % (mass fraction)Test portion (g)0,005 to 0,10 1,00,10 to 0,20 0,500,20 to 0,50 0,208.2 Blank testCarry out a blank test simultaneously with the determination, following the same procedure and using th
37、e same quantities of all reagents as used for the determination (see 8.3.2 and 8.3.3) but replacing the test solution by the iron solution (5.15). ISO 2016 All rights reserved 3BS ISO 4942:2016ISO 4942:2016(E)8.3 Determination8.3.1 Preparation of the test solutionTransfer the test portion (8.1) (see
38、 10.1) to a 250 ml beaker, cover with a watch-glass and add 20 ml to 30 ml of the hydrochloric/nitric acids mixture (5.7). When effervescence has ceased, heat gently to complete the dissolution.Add 15 ml to 20 ml of perchloric acid (5.4), raise the temperature so that white perchloric acid fumes app
39、ear and reflux in the beaker and continue fuming for about 3 min.NOTE In the case of cast irons, fuming with perchloric acid for about 3 min is not always sufficient to decompose carbides. Total decomposition is only complete when heating is continued until no more fumes are visible in the beaker an
40、d crystallization has occurred. After cooling, add about 30 ml of water and 10 ml of perchloric acid (5.4) before continuing as described below from “Add hydrogen peroxide (5.8).”.Cool, add about 30 ml of hot water and shake to dissolve salts. Add hydrogen peroxide (5.8) dropwise to reduce chromium,
41、 gradually heat to boiling and continue for 1 min to 2 min to decompose the excess of hydrogen peroxide.After cooling, filter through a medium texture filter paper and collect the filtrate in a 100 ml one-mark volumetric flask. Wash the filter paper several times with hot water. Dilute to the mark w
42、ith water and mix.8.3.2 Oxidation of vanadiumTransfer 25,0 ml of the test solution (8.3.1) into a 125 ml separating funnel. Add 2,0 ml of orthophosphoric acid (5.6) (see 10.2 and 10.3) and 5,0 ml of water and swirl.Add 0,8 ml of potassium permanganate solution (5.12), swirl and allow to stand for 4
43、min. Add 5,0 ml of urea solution (5.10) and then add 1,0 ml of sodium nitrite solution (5.9), drop by drop while swirling.Even if, after the addition of 1,0 ml of sodium nitrite solution (5.9), the solution still appears slightly pink, proceed, without any further addition of sodium nitrite solution
44、, to 8.3.3.Allow to stand for 1 min.8.3.3 Colour development and extractionAdd 25,0 ml of hydrochloric acid (5.2) and 10,0 ml of N-BPHA (5.14) and shake for 45 s.When the layers have separated, draw off the organic phase, filtering through a dry filter paper fitted in an ordinary funnel, or through
45、absorbent cotton fitted in the stem of a separating funnel, into a dry 50 ml one-mark volumetric flask.Retain the aqueous phase.Add 10,0 ml of trichloromethane (5.13) to the aqueous phase remaining in the separating funnel and shake for 30 s. Allow to settle, combine the organic phase with the main
46、extract, dilute to the mark with trichloromethane (5.13) and mix (see the following paragraph).To ensure the same colour development conditions for the test and the calibration solutions, take each solution one by one through the steps from the vanadium oxidation (8.3.2) to the extraction (8.3.3). A
47、void batch colour development and carry out each step without delay, unless otherwise specified.8.3.4 Spectrophotometric measurementsMeasure the absorbance of the test solutions at a wavelength of about 535 nm in cells of 1 cm path length, after having adjusted the spectrophotometer (6.1) to the zer
48、o absorbance against trichloromethane (5.13).4 ISO 2016 All rights reservedBS ISO 4942:2016ISO 4942:2016(E)8.4 Establishment of the calibration curve8.4.1 Preparation of the calibration solutionsTransfer 25,0 ml portions of iron solution (5.15) into a series of 125 ml separating funnels. Add the vol
49、umes of vanadium standard solution (5.17) and of water shown in Table 2, swirl and proceed as specified in 8.3.2 and 8.3.3, but omit the addition of 5 ml of water specified in 8.3.2.Table 2 Composition of the calibration solutionsVanadium standard solution (5.17) mlWater mlCorresponding vanadium concentration g/ml0 5,0 00,5 4,5 0,51,0 4,0 1,02,0 3,0 2,04,0 1,0 4,05,0 0 5,08.4.2 Spectrophotometric measurementsMeasure the absorbance of each solution at a wavelength of about 535 nm, in cells of 1 cm path len
