1、BRITISH STANDARD BS 6721-8: 1989 ISO 4743:1984 Sampling and analysis of copper and copper alloys Part 8: Method for determination of nickel in copper alloys: titrimetric method ISO title: Copper alloys Determination of nickel content Titrimetric method UDC 669.3:669.245:543.24:620.1BS6721-8:1989 Thi
2、s British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee,waspublished underthe authority of the BoardofBSI and comes into effect on 28 February 1989 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference NFM/
3、34 Draft (ref. 86/38270) announced inBSI News January 1988 ISBN 0 580 17121 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Non-ferrous Metals Standards Committee (NFM/-) to Technical Committee NFM/34 upon which the following bodies we
4、re represented: British Non-ferrous Metals Federation Copper Development Association London Metal Exchange Non-ferrous Metal Stockists Society of British Aerospace Companies Limited Coopted members The following bodies were also represented in the drafting of the standard, through subcommittees and
5、panels: BNF Metals Technology Centre British Bronze and Brass Ingot Manufacturers Association Copper Smelters and Refiners Association Ministry of Defence National Brassfoundry Association Coopted members Amendments issued since publication Amd. No. Date of issue CommentsBS6721-8:1989 BSI 12-1999 i
6、Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 2 6 Expression of results 3 7 Notes on procedure 3 8 Test report 3BS6721-8:1989 ii BSI 12-1999 National foreword This Part of BS6721 ha
7、s been prepared under the direction of the Non-ferrous Metals Standards Committee. BS6721 is a multi-part standard and describes methods of sampling and analysis for copper and copper alloys. It is intended that Parts1 to3 of BS6721 will describe methods of sampling copper and copper alloys in vario
8、us forms. The remaining Parts will give methods for the determination of individual elements in copper and copper alloys. This Part of BS6721 is identical with ISO4743:1984 “Copper alloys Determination of nickel content Titrimetric method”, published by the International Organization for Standardiza
9、tion (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the
10、 following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Part of BS 6721”. In British Standar
11、ds it is current practice to use the symbol “L” for litre (and in its submultiples) rather than “l”. The recommended name for the reagent described in3.7 (hexamethylene tetramine) is hexamine. The recommended name for the reagent described in3.10 (diacetyldioxime, commonly known as dimethylglyoxime)
12、 is butanedione dioxime. WARNING. Throughout this Part of BS 6721, normal precautions concerning the use of perchloric acid in laboratory work should be observed. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for
13、 their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 3 and a back cover. This standard has been updated (see copyright date) a
14、nd may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6721-8:1989 BSI 12-1999 1 1 Scope and field of application This International Standard specifies a titrimetric method for the determination of the nickel content of copper alloys. The m
15、ethod is applicable to contents of nickel as an alloying element in all types of copper alloys listed in International Standards. 2 Principle Separation of nickel from an ammoniacal solution of a test portion by precipitation as the diacetyldioxime complex, followed by extraction of the complex into
16、 chloroform. After evaporation of the solvent and wet digestion of the complex, determination of the nickel content by indirect complexiometric titration using voltammetric end-point indication. 3 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water
17、 or water of equivalent purity. 3.1 Ammonia, solution, 0,91g/ml. 3.2 Ammonia, solution, diluted1+10. Dilute100ml of the ammonia solution(3.1) to1100 ml with water. 3.3 Nitric acid, solution, diluted1+1. Dilute100ml of the nitric acid, 1,40g/ml with100ml of water. 3.4 Perchloric acid 1) , 1,70g/ml. 3
18、.5 Hydroxylammonium chloride (Hydroxylamine hydrochloride) 3.6 Chloroform 3.7 Hexamethylene tetramine 3.8 Tartaric acid, 500g/l solution. Dissolve500g of tartaric acid (C 4 H 6 O 6 ) in water and dilute to1000ml. 3.9 Sodium tartrate, 100g/l solution. Dissolve100g of disodium tartrate dihydrate (Na 2
19、 C 4 H 4 O 6 .2H 2 O) in water and dilute to1000ml. 3.10 Diacetyldioxime, 10g/l methanolic solution. Dissolve10g of diacetyl-dioxime (C 4 H 8 N 2 O 2 ) in methanol and dilute to1000ml with methanol. 3.11 Hydrochloric acid, solution, diluted1+1. Dilute100ml of hydrochloric acid, 1,19g/ml, to200ml wit
20、h water. 3.12 Disodiumethylenediaminetetraacetate dihydrate (Na 2 EDTA), standard volumetric solution, c(Na 2 C 10 H 14 O 8 N 2 .2H 2 O) 0,01mol/l. 3.12.1 Preparation of the solution Dissolve 3,722 g of Na 2 EDTA in water and dilute to the mark in a1000 ml one-mark volumetric flask. 3.12.2 Standardi
21、zation of the solution Pipette20,00ml of the copper solution(3.14) into a250ml beaker. Add25,00ml of the Na 2 EDTA solution(3.12.1) and adjust the pH to6,2to6,4with the hexamethylene tetramine(3.7). Add2,5ml of the MnEDTA solution(3.13) and titrate the excess EDTA with the copper solution(3.14) as s
22、pecified in5.6. The factor of the EDTA solution, F, is given by the formula where V 0 is the volume, in millilitres, of copper solution used for the determination. 3.13 Manganese(II)EDTA, solution corresponding to0,2g of Mn per litre. Dissolve0,6155g manganese (II) sulphate monohydrate (MnSO 4 .H 2
23、O),1,0642g of ethylenediamine tetraacetic acid, and10g of the hexamethylene tetramine(3.7) in200ml of water and dilute to the mark in a1000ml one-mark volumetric flask. 1ml of this solution contains0,2mg of Mn(II). NOTETo establish whether the solution contains Mn and EDTA in stoichiometric combinat
24、ion, add several milligrams of the hydroxylamine hydrochloride(3.5) and a drop of Eriochrome Black T indicator solution. The resulting colour should be a dirty pink or blue which should turn to a pure red on the addition of1drop of the copper solution (3.14) or to pure blue on the addition of1drop o
25、f the Na 2 EDTA solution(3.12). 3.14 Copper, 0,01mol/l solution. Dissolve0,6354g of copper (99,9% purity) in as little nitric acid (3.3) as necessary. Dilute to the mark in a1000ml one-mark volumetric flask. 3.15 Complexing solution Dissolve200g of ammonium acetate in500ml of water and adjust to pH9
26、 with the ammonia solution(3.1). Add400g of sodium thiosulphate and dilute to1000ml. 4 Apparatus Ordinary laboratory apparatus and 4.1 Potentiometer, equipped with a device to permit voltammetric end-point indication. NOTEThis device, which polarizes the electrodes with a constant current between1an
27、d54A, can be made simply by using an accumulator or storage battery of, for example2V in series with a1M7 resistor and the electrodes. The potentiometer is connected in parallel with the electrodes. 1) See national foreword for warning on use of perchloric acid. 20,00V 0 + 25,00 -BS6721-8:1989 2 BSI
28、 12-1999 4.2 Double platinum electrode, made of1mm diameter platinum wire, sealed in a glass tube either directly or after welding on copper wire in such a way that each wire electrode is about4mm in length with a free geometric surface of about10mm 2 . 4.3 Suction-assisted membrane filtering appara
29、tus, with ground glass joint, to fit250ml separating funnel. 4.4 Membrane filters, 14m porosity, to fit the filtering apparatus(4.3). 5 Procedure 5.1 Test portion, dissolution, and dilution Weigh, to the nearest0,001g,1,000g of finely divided sample into a 250ml tall-form beaker. Add5ml of the tarta
30、ric acid solution(3.8) and20ml of the nitric acid solution(3.3). When dissolution is complete, dilute with about30ml of water and boil for approximately5min to expel nitrous oxides. Cool to room temperature. As indicated in the table, transfer the test solution to a100ml one-mark volumetric flask if
31、 the nickel content of the sample is expected to be less than10% (m/m), or to a500ml one-mark volumetric flask if the nickel content is expected to be10% (m/m) or greater. Dilute to the mark with water and mix. According to the expected nickel content, pipette an aliquot portion of the diluted test
32、solution into a250ml beaker, as indicated in the table. Dilute, if necessary, to50ml with water. 5.2 Complex formation Add, in sequence, the following, mixing after each addition: 10 ml of the sodium tartrate solution(3.9); ammonia solution(3.1) until all of the nickel and copper present are redisso
33、lved; hydroxylamine hydrochloride(3.5) until the solution is decolorized (0,1to0,2g, depending on the amount of copper present); 20ml of the complexing solution(3.15) (30 ml if an aliquot corresponding to more than0,2g of the sample was taken); 15ml of the diacetyldioxime solution(3.10). 5.3 Filtrat
34、ion and first extraction Filter the precipitate through a14m membrane filter directly into a250ml separating funnel using a Witts filter apparatus(4.3). Wash the beaker three times with5ml of the ammonia solution(3.2) and twice with5ml of water. Shake the filtrate with25ml of the chloroform(3.6), re
35、serving the organic phase. Repeat the extraction with20ml of the chloroform. Combine the organic extracts. 5.4 Treatment of precipitate Dissolve the filter in10ml of the nitric acid solution(3.3), and repeat the precipitation of nickel and the extraction of the filtrate as specified in5.2 and5.3. 5.
36、5 Digestion Dissolve the filter from5.4 in a250ml beaker containing10ml of the nitric acid solution(3.3) and combine with the four chloroform extracts. Add several boiling chips and evaporate the solution to a volume of about2ml. Remove the chips and wash them with a few millilitres of water. Add2ml
37、 of the perchloric acid(3.4) to the solution and fume to near-dryness (0,5ml). Cool the residue. 5.6 Titration Dissolve the residue with20ml of water and add the Na 2 EDTA solution (3.12) as indicated in the table. Adjust the pH to6,26,4with hexamethylene tetramine(3.7). Add2,5ml of the Mn(II)EDTA s
38、olution(3.13) and titrate the excess EDTA with the copper solution(3.14), using the voltammetric indication with the polarized double-platinum electrode(4.2). The copper solution should be added drop by drop, rapidly at first, then slowly as the end-point is approached. The end-point will be indicat
39、ed by a very sharp potential break of about250mV per drop. 5.7 Check test Make a preliminary check of the potentiometric apparatus by preparing a solution of a standard material or a synthetic sample containing a known amount of nickel and of composition similar to the material to be analysed, and c
40、arrying out the procedure as specified in5.1 to5.6. Expected nickel content Dilution Aliquot Mass of sample in solution Volume of Na 2EDTA solution (3.12) to be added % (m/m) ml ml g ml 2 5 10 20 40 60 100 100 500 500 500 500 50 20 50 50 25 20 0,5 0,2 0,1 0,1 0,05 0,04 25 25 25 50 50 50BS6721-8:1989
41、 BSI 12-1999 3 6 Expression of results 6.1 Calculation The nickel content, expressed as a percentage by mass, is given by the formula where V 1 is the volume, in millilitres, of the Na 2 EDTA solution(3.13) added; V 2 is the volume, in millilitres, of the copper solution(3.15) required for the titra
42、tion; F is the factor of the Na 2 EDTA solution(3.12), as calculated in3.12.2; m is the mass, in grams, of the sample in the test solution; 0,000 587is the mass, in grams, of nickel corresponding to1ml of the Na 2 EDTA solution(3.12). Express the result to two decimal places. 6.2 Repeatability and r
43、eproducibility Comparative tests carried out on the same sample by laboratories gave the following statistical data: 7 Notes on procedure 7.1 Preparation of electrodes At the end-point of the titration, the anode will be coated with manganese(II) dioxide. This coating must be dissolved after each ti
44、tration by dipping the electrode into a solution of hydrochloric acid (1+5) containing some hydrogen peroxide. 7.2 Visual indicator A visual indicator can be used instead of the voltammetric method, but a decrease in accuracy results. Xylenol orange, ground1:50with potassium nitrate, is suitable. A0
45、,01mol/l zinc solution should be used as the titrant rather than copper. 8 Test report The test report shall include the following particulars: a) an identification of the sample; b) the reference of the method used; c) the results and the method of expression used; d) any unusual features noted dur
46、ing the determination; e) any operation not included in this International Standard, or regarded as optional, which might affect the results. Characteristic Value Average Ni content,% (m/m): 43,36 Standard deviation of repeatability, r : 0,045 of reproducibility, R : 0,097 BS 6721-8: 1989 ISO 4743:1
47、984 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards
48、are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this
49、BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001. Fax:02089967001. In response to orders fo
