1、BRITISH STANDARD BS 6200-3.31.1: 1992 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section 3.31 Determination of tin Subsection 3.31.1 Steel and cast iron: volumetric methodBS6200-3.31.1:1992 This British Standard, having been prepared under the directiono
2、f 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 comment91/44343DC ISBN 0 580 20799 4 Committee
3、s 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 Industry (Labo
4、ratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.31.1:1992 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Ap
5、paratus 1 5 Sampling 2 6 Procedure 2 7 Calculation and expression of results 3 8 Test report 4 Table 1 Precision data 3 Publication(s) referred to Inside back coverBS6200-3.31.1:1992 ii BSI 09-1999 Foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standar
6、ds Policy Committee and supersedes method1 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 ferrous metals. A list of contents, together with g
7、eneral 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 itself confer immunity from legal obligations. Su
8、mmary 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 indicated in the amendment table on the inside fron
9、t cover.BS6200-3.31.1:1992 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a volumetric method for the determination of tin in steel and cast iron. The method is applicable to tin contents from0.005% (m/m) to0.25% (m/m). NOTEThe titles of the publications referred to in this Subsection of
10、BS6200 are listed on the inside back cover. 2 Principle The sample is dissolved in hydrochloric acid and, with sulfurous acid present to maintain reducing conditions, the solution is filtered to remove insoluble carbides. From the filtrate, tin is precipitated as sulfide together with molybdenum sul
11、fide 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 carrier. The precipitate is dissolved in acid and tin reduced to the divalent state with metallic aluminium in the prese
12、nce 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 analytical grade and only grade3 water as specified in BS3978. WARNING. Prepare the solutions of bromine, hydrogen sulfid
13、e and sulfur dioxide in a fume cupboard. 3.1 Aluminium metal. Use a commercial grade, free from tin, in the form of heavy foil, coarse millings, or drillings. Commercially pure aluminium (tin free) dissolves more readily than the purer grades. 3.2 Ammonia solution, density =0.91g/ml, diluted1+1. 3.3
14、 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. 3.4 Antimony trichloride,10g/1 solution. Dissolve1g of antimony trichloride in20ml of hydrochloric acid(3.6) and20ml of water, cool, dilute to100ml and mix. 3.5 Bromine
15、water, saturated solution. To100ml of water, add5ml of bromine, shake and allow to stand until saturated. 3.6 Hydrochloric acid, =1.16g/ml to1.18g/ml. 3.7 Hydrochloric acid, =1.16g/ml to1.18g/ml, diluted1+1. 3.8 Hydrochloric acid, =1.16g/ml to1.18g/ml, diluted1+19. 3.9 Hydrogen sulfide, gas, from a
16、generator or cylinder. 3.10 Hydrogen sulfide-sulfuric acid wash. To900ml of water, cautiously add10ml of sulfuricacid(3.17), dilute to1l and pass a rapid stream of hydrogen sulfide gas(3.9) through the solution for not less than10min. 3.11 Iron(III) chloride solution. Dissolve0.5g of high purity iro
17、n, free from tin, in20ml of hydrochloric acid(3.6), heat to boiling, oxidize with the minimum amount of nitric acid(3.12) and continue boiling to expel nitrous fumes. Cool, dilute to100ml and mix. 3.12 Nitric acid, =1.42g/ml. 3.13 Potassium iodate, standard solution, equivalent to0.5935mg tin per mi
18、llilitre. Dissolve0.3567g of potassium iodate, previously dried to constant weight at105 C, in freshly boiled and cooled water. Cool, transfer to a1l volumetric flask, dilute to the mark and mix. This reagent shall be as free from dissolved oxygen as possible. Use only freshly boiled and cooled wate
19、r in its preparation. 3.14 Potassium iodide,100g/l solution. Dissolve10g of potassium iodide in freshly boiled and cooled water, dilute to100ml and mix. This reagent shall be as free from dissolved oxygen as possible. Use only freshly boiled and cooled water in its preparation. 3.15 Sodium hydrogen
20、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 dissolved oxygen as possible. Use only freshly boiled and cooled water in its preparation. 3.16 Starch indicator,5g/l solution. Make a suspe
21、nsion of0.5g of starch in10ml of water. Pour into90ml of boiling water. Cool, dilute to100ml and mix. 3.17 Sulfuric acid, =1.84g/ml. 3.18 Sulfurous acid. Pass sulfur dioxide gas into1l of water until a saturated solution is obtained. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glass
22、ware, in accordance with classA of BS846, BS1583 or BS1792, as appropriate.BS6200-3.31.1:1992 2 BSI 09-1999 4.3 Tin reduction 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 flas
23、k is fitted with a rubber bung holding a glass syphon tube of approximately6mm bore that protrudes approximately10mm to15mm into the flask below the base of the bung and externally is bent over to overhang the edge of the hot plate. 5 Sampling Carry out sampling in accordance with BS1837. NOTEBS6200
24、-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 of5.0g. 6.2 Blank test In parallel with the determination and fol
25、lowing 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 a650ml conical beaker, add60ml of hydrochloric acid(3.6) and10ml of sulfurous acid(3.18), cover the beaker and digest at a t
26、emperature not exceeding65 C until solvent action ceases. Add100ml of hot water,25ml of sulfurous acid(3.18), a little ashless paper-pulp and boil for5min. Allow to stand for a few minutes. For steels containing niobium, tungsten or tantalum extend the standing time to2h. Then filter through a paper
27、-pulp pad, as far as possible by decantation. Wash with hot hydrochloric acid(3.8) containing a few drops of sulfurous acid(3.18) and discard the residue. 6.3.2 Co-precipitation of tin and molybdenum sulphides To the filtrate, add5ml of bromine water(3.5) and boil for a few minutes. Cool and careful
28、ly neutralize with ammonia solution(3.2) until a faint permanent precipitate of hydroxide is formed. Add hydrochloric acid(3.6), dropwise, until the precipitate is just redissolved, then add10ml excess and dilute to approximately450ml. Add2ml of ammonium molybdate solution(3.3), heat to boiling and,
29、 in a fume cupboard, pass a rapid stream of hydrogen sulfide(3.9) through the solution 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(3.10). Return the pad and precipitate to the beaker in
30、which the precipitation was made, add25ml of nitric acid(3.12) and10ml of sulfuric acid(3.17), then evaporate to fuming. If necessary make further additions of nitric acid(3.12) and repeat the evaporation to fuming until organic matter is destroyed. Cool, add100ml of water and15ml of hydrochloric ac
31、id(3.6), then heat until soluble salts are dissolved. If tungsten is present a small amount of tungstic acid may precipitate at this stage; in this case filter through a paper-pulp pad and wash with hydrochloric acid(3.8). 6.3.3 Co-precipitation of tin and iron hydroxides Add5ml of iron(III) chlorid
32、e solution(3.11) and heat to boiling. Remove from the source of heat and cautiously add ammonia solution(3.2) 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 with140
33、ml of hot hydrochloric acid(3.7), collecting the solution in the500ml conical flask(4.3). Finally wash several times with hot hydrochloric acid(3.8) until a total volume of approximately200ml is collected. 6.3.4 Reduction of tin Add2ml of antimony trichloride solution(3.4), heat nearly to boiling an
34、d make small additions of tin-free aluminium(3.1) until approximately1g has been added. Before the last addition 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 f
35、or discard. Immerse the end of the syphon tube in200ml of sodium hydrogen carbonate solution(3.15) contained in a250ml tall-form beaker. Remove the assembly from the hot plate and allow the sodium hydrogen carbonate solution(3.15) to be drawn back into the flask to evolve carbon dioxide. Cool to bel
36、ow20 C, keeping the end of the syphon tube immersed. 6.3.5 Titration of tin Remove the bung from the flask, add10ml of potassium iodide solution(3.14) and5ml of starch indicator(3.16). Titrate immediately with potassium iodate solution(3.13) until a permanent blue end-point is reached. Record the vo
37、lume V tof potassium iodate solution(3.13) used. Titrate the blank test in the same manner, and record the volume V bof potassium iodate solution(3.13) used.BS6200-3.31.1:1992 BSI 09-1999 3 7 Calculation and expression of results 7.1 Calculation NOTE1ml of potassium iodate solution(3.13) is equivale
38、nt to0.5935mg of tin. Calculate the tin content Sn expressed as a percentage by mass from the equation: Sn =0.05935(V t V b )/m 7.2 Precision Planned trials of this method were carried out by eight to ten analysts, each from a different laboratory; usually three tests were carried out by each analys
39、t on each of eight steels. For three steels where individual results are given in the original reports 1),2) , the95% confidence limits(2s) have been calculated in accordance with BS5497-1 and are given in Table 1. The difference between two single results found on identical material by one analyst
40、using the same apparatus within a short time 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 ide
41、ntical test material will exceed the reproducibility R, on average, not more than once in20cases in the normal and correct operation of the method. For five steels where only laboratory means are reported, it is not possible to calculate repeatabilityr and reproducibility R. Therefore from these res
42、ults, for probability P =95%, the statistical limits(2.83s) for agreement between laboratory means have been calculated and are also given in Table 1. The difference between the mean results of two laboratories found on identical test material will exceed the P=95% probability level, on average, not
43、 more than once in20cases in the normal and correct operation of the method. The correlations from regression analyses of repeatability r and reproducibility R with tin concentration have probabilities too low to justify predictions of precision. The original reports included additional results from
44、 this procedure with minor experimental variations and the precision suggested overall was as follows: with0.05% (m/m) tin present: 0.003%(m/m) with0.20% (m/m) tin present: 0.006%(m/m). Table 1 Precision data where V t is the volume of potassium iodate solution(3.13) used in6.3.5 in the titration of
45、 the test portion (in ml); V b is the volume of potassium iodate solution(3.13) used in6.3.5 in the titration of the blank (in ml); m is the mass of the test portion (in g). 1) Methods of Analysis Committee. Determination of tin in highly alloyed steels. Journal of the Iron and Steel Institute 165,
46、June1950,190197. 2) Methods of Analysis Committee. Determination of tin. Journal of the Iron and Steel Institute 176, February1954,156157. Type of steel Approximate composition Tin Repeatability r Reproducibility R % (m/m) Mild steel,0.05%Mo Mild steel,0.2%Cu 3%Ni Cr steel % (m/m) 0.029 0.029 0.171
47、0.0028 0.0032 0.0129 0.0058 0.0077 0.0207 Between-laboratory agreement2s 13Ni,13Cr,10Co,3W,3Nb,2Mo 2C,14Cr,0.5W 2C,2Ni,18Cr,2Co,2W 30Ni,20Cr,1.5Ti 7Ni,18Cr,3W,1.5Nb,1Ti,1V,1Zr 0.015 0.016 0.028 0.025 0.247 0.0024 0.0050 0.0053 0.0037 0.0043BS6200-3.31.1:1992 4 BSI 09-1999 8 Test report The test repo
48、rt 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 the form in which they are expressed; d) any unusual features not
49、ed during the determination; e) any operation not specified in this British Standard or any optional operation which may have influenced the results.BS6200-3.31.1:1992 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 ferro-alloys. BS3978, Specification for water for laboratory use. BS5497, Precision of test methods. BS5497-1, Guide for the deter
