1、BRITISH STANDARD BS 6200-3.31.2: 1992 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section3.31 Determination of tin Subsection3.31.2 Ferrotungsten and tungsten metal: volumetric methodBS6200-3.31.2:1992 This British Standard, having been prepared under the
2、 directionof the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15June1992 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment91/44344 DC ISBN 0 580 20800
3、 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/18, upon which the following bodies were represented: BCIRA British Steel Industry Department of Trade and In
4、dustry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.31.2:1992 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Rea
5、gents 1 4 Apparatus 1 5 Sampling 2 6 Procedure 2 7 Calculation and expression of results 3 8 Test report 3 Table 1 Precision data 3 Table 2 Predicted values of r and R 3 Publication(s) referred to Inside back coverBS6200-3.31.2:1992 ii BSI 09-1999 Foreword This Subsection of BS6200 has been prepared
6、 under the direction of the Iron and Steel Standards Policy Committee and supersedes method2 for the determination of tin in BSI Handbook No.19, to which it is technically equivalent. BS6200 is a multipart British Standard, covering all aspects of the sampling and analysis of iron, steel and other f
7、errous metals. A list of contents, together with general information, is given in Part1. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of
8、 itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be i
9、ndicated in the amendment table on the inside front cover.BS6200-3.31.2:1992 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a volumetric method for the determination of tin in ferrotungsten and tungsten metal. The method covers the range of tin contents normally found in ferrotungsten and
10、 tungsten metal. NOTEThe titles of the publications referred to in this Subsection of BS6200 are listed on the inside back cover. 2 Principle A solution of the sample in sulfuric, hydrofluoric and nitric acids is evaporated to fuming. The fumed concentrate is extracted in citric acid, and the tungst
11、en complexed by digestion in ammoniacal citrate solution. Tin is precipitated as sulfide together with molybdenum sulfide as a carrier. The precipitate and filter are decomposed by wet oxidation and tin is precipitated as hydroxide from ammoniacal solution together with a small amount of iron as car
12、rier. The precipitate is dissolved in acid and tin reduced to the divalent state with metallic aluminium in the presence of an antimony salt. The determination is completed volumetrically by titration with potassium iodate solution. 3 Reagents During the analysis use only reagents of recognized anal
13、ytical grade and only water of grade3 as specified in BS3978. WARNING. Prepare the solution of hydrogen sulfide in a fume cupboard. 3.1 Aluminium metal, commercial grade, free from tin, in the form of heavy foil, coarse millings, or drillings. Commercially pure aluminium (tin free) dissolves more re
14、adily than the purer grades. 3.2 Ammonia solution, density =0.91g/ml. 3.3 Ammonia solution, =0.91g/ml, diluted1+1. 3.4 Ammonium molybdate,10g/l solution. Dissolve10g of ammonium molybdate(NH 4 ) 6 Mo 7 O 24 .4H 2 O, in water, dilute to1l and mix. 3.5 Antimony trichloride,10g/l solution. Dissolve1g o
15、f antimony trichloride in20ml of hydrochloric acid(3.7) and20ml of water, cool, dilute to100ml and mix. 3.6 Citric acid,200g/l solution. Dissolve200g of citric acid in600ml of water, dilute to1l, and mix. 3.7 Hydrochloric acid, =1.16g/ml to1.18g/ml. 3.8 Hydrochloric acid, =1.16g/ml to1.18g/ml, dilut
16、ed1+1. 3.9 Hydrochloric acid, =1.16g/ml to1.18g/ml, diluted1+19. 3.10 Hydrofluoric acid,40% (m/m). 3.11 Hydrogen sulfide, gas, from a generator or cylinder. 3.12 Hydrogen sulfide-sulfuric acid wash. To900ml of water, cautiously add10ml of sulfuric acid(3.19), dilute to1l and pass a rapid stream of h
17、ydrogen sulfide gas(3.11) through the solution for not less than10min. 3.13 Iron(III) chloride solution. Dissolve0.5g of high purity iron, free from tin, in20ml of hydrochloric acid(3.7), heat to boiling, oxidize with the minimum amount of nitric acid(3.14) and continue boiling to expel nitrous fume
18、s. Cool, dilute to100ml and mix. 3.14 Nitric acid, =1.42g/ml. 3.15 Potassium iodate, standard solution, equivalent to0.5935mg of tin per millilitre. Dissolve0.3567g of potassium iodate, previously dried to constant weight at105 C, in freshly boiled and cooled water. Cool, transfer to a1l volumetric
19、flask, dilute to the mark and mix. This reagent shall be as free from dissolved oxygen as possible. Use only freshly boiled and cooled water in its preparation. 3.16 Potassium iodide,100g/l solution. Dissolve10g of potassium iodide in freshly boiled and cooled water, dilute to100ml and mix. This rea
20、gent shall be as free from dissolved oxygen as possible. Use only freshly boiled and cooled water in its preparation. 3.17 Sodium hydrogen carbonate,100g/l solution. Dissolve100g of sodium hydrogen carbonate in freshly boiled and cooled water, dilute to1l and mix. This reagent shall be as free from
21、dissolved oxygen as possible. Use only freshly boiled and cooled water in its preparation. 3.18 Starch indicator,5g/l solution. Make a suspension of0.5g of starch in10ml of water. Pour into90ml of boiling water. Cool, dilute to100ml and mix. 3.19 Sulfuric acid, =1.84g/ml. 3.20 Sulfuric acid, =1.84g/
22、ml, diluted1+1. To40ml of water, add cautiously50ml of sulfuric acid(3.19). Mix, cool, dilute to100ml and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS846, BS1583 or BS1792, as appropriate.BS6200-3.31.2:1992 2 BSI 09-1999 4.3 Tin reducti
23、on apparatus. A suitable assembly for carrying out the reduction of tin consists of a500ml conical flask marked at200ml and having a neck of approximately25mm diameter. The flask is fitted with a rubber bung holding a glass syphon tube of approximately6mm bore that protrudes approximately10mm to15mm
24、 into the flask below the base of the bung and externally is bent over to overhang the edge of the hot plate. 4.4 Platinum vessel, with cover, for example a crucible of50ml capacity or alternatively a dish of100ml capacity. 4.5 Radiant heater 5 Sampling Carry out sampling in accordance with BS1837.
25、NOTEBS6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS6200-2. 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of2.0g. If the tin content exceeds0.6% (m/m) weigh a pr
26、oportionately smaller test portion. 6.2 Blank test In parallel with the determination and following the same procedure, carry out a blank test using the same quantities of all reagents. 6.3 Determination 6.3.1 Preparation of the test solution Place the test portion in the platinum vessel(4.4), add5m
27、l of sulfuric acid(3.20),5ml of hydrofluoric acid(3.10) and then nitric acid(3.14) a few drops at a time, covering the vessel after each addition, until solvent action ceases. Rinse the cover and vessel with water and add10ml of sulfuric acid(3.20). Evaporate to fuming under the radiant heater(4.5).
28、 Continue fuming lightly for approximately1h to ensure removal of both fluoride and nitrate. Allow to cool and extract in100ml of citric acid(3.6) contained in a600ml squat beaker. Rinse and remove the vessel. Neutralize with ammonia solution(3.2) and add10ml excess. Heat to ensure solution of tungs
29、tic acid, acidify with sulfuric acid(3.20), then add5ml excess and dilute to approximately450ml. 6.3.2 Co-precipitation of tin and molybdenum sulfides Add2ml of ammonium molybdate solution(3.4), heat to boiling and, in a fume cupboard, pass a rapid stream of hydrogen sulfide(3.11) through the soluti
30、on for1h. Allow to stand for at least2h, preferably overnight. Filter through a paper-pulp pad and wash the precipitate with hydrogen sulfide-sulfuric acid wash(3.12). Return the pad and precipitate to the beaker in which the precipitation was made, add25ml of nitric acid(3.14) and10ml of sulfuric a
31、cid(3.19), then evaporate to fuming. If necessary make further additions of nitric acid(3.14) and repeat the evaporation to fuming until organic matter is destroyed. Cool, add100ml of water and15ml of hydrochloric acid(3.7), then heat until soluble salts are dissolved. A small amount of tungstic aci
32、d may precipitate at this stage; in this case filter through a paper-pulp pad and wash with hydrochloric acid(3.9). 6.3.3 Co-precipitation of tin and iron hydroxides Add5ml of iron(III) chloride solution(3.13) and heat to boiling. Remove from the source of heat and cautiously add ammonia solution(3.
33、3) until the solution is just alkaline. Filter through a hardened12.5cm paper and wash with hot water. NOTEA Whatman No.541 paper is suitable. Dissolve the precipitate through the paper with140ml of hot hydrochloric acid(3.8), collecting the solution in the500ml conical flask(4.3). Finally wash seve
34、ral times with hot hydrochloric acid(3.9) until a total volume of approximately200ml is collected. 6.3.4 Reduction of tin Add2ml of antimony trichloride solution(3.5), heat nearly to boiling and make small additions of tin-free aluminium(3.1) until approximately1g has been added. Before the last add
35、ition of aluminium has dissolved fit the bung and syphon tube(4.3) to the flask, then heat the solution to boiling and continue boiling for30min, allowing the condensate to drip into a beaker for discard. Immerse the end of the syphon tube in200ml of sodium hydrogen carbonate solution(3.17) containe
36、d in a250ml tall-form beaker. Remove the assembly from the hot plate and allow the sodium hydrogen carbonate solution(3.17) to be drawn back into the flask to evolve carbon dioxide. Cool to below20 C, keeping the end of the syphon tube immersed. 6.3.5 Titration of tin Remove the bung from the flask,
37、 add10ml of potassium iodide solution(3.16) and5ml of starch indicator(3.18). Titrate immediately with potassium iodate solution(3.15) until a permanent blue end-point is reached. Record the volume V tof potassium iodate solution(3.15) used.BS6200-3.31.2:1992 BSI 09-1999 3 Titrate the blank test in
38、the same manner, and record the volume V bof potassium iodate solution(3.15) used. 7 Calculation and expression of results 7.1 Calculation NOTE1ml of potassium iodate solution(3.15) is equivalent to0.5935mg of tin. Calculate the tin content Sn, expressed as a percentage by mass, from the equation: S
39、n =0.05935(V t V b )/m where 7.2 Precision 7.2.1 Precision data Planned trials of this method were carried out by six to nine analysts, each from a different laboratory; up to three tests were carried out by each analyst on each of three samples of ferrotungsten and one of tungsten metal, with65 res
40、ults in total. From the original report 1) , the95% confidence limits (2s) have been calculated in accordance with BS5497-1 and are given in Table 1. Table 1 Precision data The difference between two single results found on identical material by one analyst using the same apparatus within a short ti
41、me interval will exceed the repeatability r, on average, not more than once in20cases in the normal and correct operation of the method. The difference between two single and independent results found by two operators working in different laboratories on identical test material will exceed the repro
42、ducibility R, on average, not more than once in20cases in the normal and correct operation of the method. 7.2.2 Regression data Statistical analysis of the results showed a logarithmic relationship between the tin content and the values of repeatability r and reproducibility R summarized by the foll
43、owing logarithmic regression equations. log r =0.4885log Sn 1.6803 correlation coefficient=0.990 log R=0.4832log Sn1.4338 correlation coefficient=0.931 with tin content Sn, r and R expressed as a percentage by mass. The predicted values of r and R calculated from these equations are shown in Table 2
44、. Table 2 Predicted values of r and R 8 Test report The test report shall include the following information: a) all information necessary for the identification of the sample, the laboratory and the date of analysis; b) the method used, by reference to this Subsection of BS6200; c) the results, and
45、the form in which they are expressed; d) any unusual features noted during the determination; e) any operation not specified in this British Standard or any optional operation which may have influenced the results. V t is the volume of potassium iodate solution(3.15) used in6.3.5 in the titration of
46、 the test portion (in ml); V b is the volume of potassium iodate solution(3.15) used in6.3.5 in the titration of the blank (in ml); m is mass of the test portion (ing). 1) Methods of Analysis Committee. Determination of tin in ferrotungsten and tungsten metal. Journal of the Iron and Steel Institute
47、 168, May1951,5156. Sample Tin Repeatability r Reproducibility R A B C D % (m/m) 0.011 0.055 0.123 0.597 0.0023 0.0047 0.0089 0.0152 0.0052 0.0057 0.0138 0.0342 Tin Repeatability, r Reproducibility, R % (m/m) 0.010 0.020 0.050 0.10 0.20 0.50 0.0022 0.0031 0.0048 0.0068 0.0095 0.0149 0.0040 0.0056 0.
48、0087 0.0121 0.0169 0.02634 blankBS6200-3.31.2:1992 BSI 09-1999 Publication(s) referred to BS846, Specification for burettes. BS1583, Specification for one-mark pipettes. BS1792, Specification for one-mark volumetric flasks. BS1837, Methods for the sampling of iron, steel, permanent magnet alloys and
49、 ferro-alloys. BS3978, Specification for water for laboratory use. BS5497, Precision of test methods. BS5497-1, Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. BS6200, Sampling and analysis of iron, steel and other ferrous metals. BS6200-1, Introduction and contents 2) . BS6200-2, Methods of sampling and sample preparation 3) . BSI Handbook No.19 2)Methods for the sampling and analysis of iron, steel and other ferrous metals. 2) Referred to in the foreword only. 3) In prep
