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1、BRITISH STANDARD BS 6200-3.33.1: 1992 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.33 Determination of tungsten Subsection 3.33.1 Steel: gravimetric method Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrol
2、led Copy, (c) BSI BS 6200-3.33.1:1992 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 June 1992 BSI 09-1999 The following BSI references relate to th
3、e work on this standard: Committee reference ISM/18 Draft for comment 91/44345 DC ISBN 0 580 20801 X 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 wh
4、ich the following bodies were represented: BCIRA British Steel Industry Department of Trade and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffi
5、eldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.1:1992 BSI 09-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3Reagents1 4Apparatus1 5Sampling2 6Procedure2 7Calculation and expression of results3 8Test report5 Table 1
6、 Molybdenum calibration data2 Table 2 Precision data4 Table 3 Values for inter-laboratory agreement (2.83 Sb, P = 95 %)5 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.1:1992 ii BSI 0
7、9-1999 Foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method 1 for the determination of tungsten in BSI Handbook No. 19, to which it is technically equivalent. BS 6200 is a multipart British Standard, covering
8、 all aspects of the sampling and analysis of iron, steel and other ferrous metals. A list of contents, together with general information, is given in Part 1. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for thei
9、r 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, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see
10、 copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.1:1992 BSI 09-19991 1 Scope This Subsection of B
11、S 6200 describes a gravimetric method for the determination of tungsten in steel. It is suitable for steel containing 3 % (m/m) to 30 % (m/m) tungsten but is not applicable to steels containing niobium and/or tantalum. NOTEThe titles of the publications referred to in this Subsection of BS 6200 are
12、listed on the inside back cover. 2 Principle A solution of the test portion in hydrochloric acid is oxidized to decompose carbides, then reduced with sulfurous acid and the tungsten separated by hydrolysis, cinchonine being used as an auxiliary precipitant. The precipitate is ignited and weighed aft
13、er removing silica by volatilization with hydrofluoric acid. Corrections are made for impurities in the tungsten trioxide. 3 Reagents During the analysis use only reagents of recognized analytical grade and only grade 3 water as specified in BS 3978. 3.1 Ammonium citrate, 500 g/l solution. Dissolve
14、500 g of citric acid, H8C6O7.H2O, in 500 ml of ammonia solution (3.2), cool, dilute to 1 l and mix. 3.2 Ammonia solution, density = 0.91 g/ml. 3.3 Ammonia solution, = 0.91 g/ml, diluted 1 + 1. 3.4 Ammonium nitrate, 20 g/l solution. Dissolve 20 g of ammonium nitrate in water, dilute to 1 l and mix. 3
15、.5 Ammonium thiocyanate, 200 g/l solution. Dissolve 20 g of ammonium thiocyanate in 70 ml of water, dilute to 100 ml and mix. 3.6 n-Butyl acetate, in accordance with BS 551. 3.7 Cinchonine hydrochloride, 100 g/l solution. Dissolve 10 g of cinchonine hydrochloride in 100 ml of hydrochloric acid (3.10
16、). 3.8 Cinchonine wash solution. Add 20 ml of cinchonine hydrochloride solution (3.7) and 20 ml of hydrochloric acid (3.9) to 500 ml of water, dilute to 1 l and mix. 3.9 Hydrochloric acid, = 1.16 g/ml to 1.18 g/ml. 3.10 Hydrochloric acid, = 1.16 g/ml to 1.18 g/ml, diluted 1 + 1. 3.11 Hydrofluoric ac
17、id, 40 % (m/m). 3.12 Iron, high purity, free from molybdenum. 3.13 Molybdenum, standard solution, 0.5 mg of molybdenum per millilitre. Dissolve 0.5 g of high purity molybdenum in a mixture of 10 ml of sulfuric acid (3.18), 5 ml of nitric acid (3.14) and 5 ml of water. Cool, transfer to a 1 1 volumet
18、ric flask, dilute to the mark and mix. 3.14 Nitric acid, = 1.42 g/ml. 3.15 Orthophosphoric acid, = 1.75 g/ml, diluted 1 + 1. 3.16 Potassium dichromate, standard solution, equivalent to 0.1 mg of chromium(III) oxide per millilitre. Dissolve 0.1935 g of potassium dichromate, previously dried to consta
19、nt weight at 150 C, in approximately 500 ml of water. Cool, transfer to a 1 l volumetric flask, dilute to the mark and mix. 3.17 Sodium carbonate, anhydrous. 3.18 Sulfuric acid, = 1.84 g/ml, diluted 1 + 1. To 400 ml of water, add cautiously, with cooling and stirring, 500 ml of sulfuric acid = 1.84
20、g/ml. Cool, dilute to 1 l and mix. 3.19 Sulfurous acid. In a fume cupboard, pass sulfur dioxide into 1 l of water until a saturated solution is obtained. 3.20 Tin(II) chloride, 200 g/l solution. Dissolve 20 g of tin(II) chloride, SnCl2.2H2O, in 20 ml of hydrochloric acid (3.9) and warm until a clear
21、 solution is obtained. Cool, dilute to 100 ml with water and mix. 3.21 Titanium sulfate-acid mixture. Dissolve 1.5 g of high purity titanium in a mixture of 180 ml of water and 25 ml of sulfuric acid, = 1.84 g/ml. To 200 ml of water add cautiously, while stirring, 160 ml of perchloric acid, = 1.54 g
22、/ml, and 105 ml of sulfuric acid, = 1.84 g/ml. Cool and combine the two solutions, dilute to 1 l and mix. 3.22 Vanadotungstic acid, standard solution, 0.1 mg of vanadium pentoxide per millilitre. Dissolve 0.1286 g of ammonium metavanadate, 4 g of tungsten trioxide and 10 g of sodium hydroxide in wat
23、er and boil until free from ammonia. Cool, neutralize with orthophosphoric acid (3.15) and add 50 ml excess. Cool, transfer to a 1 l volumetric flask, dilute to the mark and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with class A of BS 846, BS 1583 or
24、BS 1792, as appropriate. 4.3 Platinum dish 4.4 Spectrophotometer, suitable for the measurement of absorbance at a wavelength of 550 nm. 4.5 Cells, having an optical path length of 1.0 cm. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 62
25、00-3.33.1:1992 2 BSI 09-1999 5 Sampling Carry out sampling in accordance with BS 1837. NOTEBS 6200-2, which will supersede BS 1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS 6200-2. 6 Procedure 6.1 Test portion Weigh, to
26、 the nearest 0.001 g, a test portion of 2.0 g. 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 Preparation of the test solution Place the test portion in a 600 ml squat beaker. Add 60 ml of hydr
27、ochloric acid (3.9), cover the beaker and heat until solvent action ceases. Evaporate to dryness and bake lightly for 5 min. Cool, add 60 ml of hydrochloric acid (3.9), heat gently until the salts are dissolved and oxidize with nitric acid (3.14), added dropwise. Evaporate to approximately 15 ml, ad
28、d 30 ml of hydrochloric acid (3.9) and evaporate again to approximately 15 ml, taking care to avoid localized drying out of iron salts. Cool, add 100 ml of sulfurous acid (3.19), mix by swirling and heat to boiling. Boil for 2 min to 3 min, dilute to 250 ml with hot water, add a small amount of pape
29、r-pulp and 5 ml of cinchonine hydrochloride solution (3.7). Boil for 3 min, remove from the source of heat and allow to stand overnight. Filter through a paper-pulp pad and wash with cinchonine wash solution (3.8). Transfer the filter and precipitate to a platinum dish (4.3). Remove any adhering fil
30、m of tungsten trioxide from the side of the beaker by scouring with a piece of ashless paper moistened with ammonia solution (3.3) and add to the dish. 6.4 Treatment of the precipitate Ignite at a low temperature until freed from carbonaceous matter, and finally at a temperature not exceeding 800 C.
31、 Cool, moisten the residue with water, add 5 ml of hydrofluoric acid (3.11), and evaporate to dryness. Ignite at a temperature not exceeding 800 C, cool in a desiccator and weigh. Record the mass, m1. Mix the residue with 5 g of sodium carbonate (3.17) with a smooth rounded pestle and fuse at approx
32、imately 1 000 C for 5 min. Cool, extract the melt by boiling with 100 ml of water and simmer for 1 h to coagulate insoluble matter. Filter through a paper-pulp pad and wash with hot ammonium nitrate solution (3.4). Dissolve any residue adhering to the platinum dish by warming with a few drops of hyd
33、rochloric acid (3.9), make the solution alkaline with ammonia solution (3.3) and collect the precipitate on the filter holding the insoluble matter. Retain both filter and filtrate. Transfer the filter and residue to the platinum dish (4.3), ignite at approximately 800 C, cool in a desiccator and we
34、igh. Record the mass, m2. Cool the fusion filtrate, transfer to a 250 ml volumetric flask, dilute to the mark and mix. Reserve for use for the determination of the oxides of chromium, molybdenum and vanadium present as impurities in the tungsten trioxide (see 6.5). 6.5 Determination of chromium, mol
35、ybdenum and vanadium oxides in the filtrate 6.5.1 General Determine impurities in the residue on suitable aliquots of the solution from 6.4 as described in 6.5.2, 6.5.3 and 6.5.4, using the solution from the reagent blank as the compensating blank for the chromium oxide and vanadium oxide determinat
36、ions. 6.5.2 Chromium(III) oxide Transfer equal volumes (100 ml or less) of the test portion and blank solution fusion filtrates (see 6.4) to 400 ml squat beakers. Add potassium dichromate solution (3.16) to the blank solution until the colour matches that of the test portion solution. Record the vol
37、ume of the aliquot used V1 and the volume of potassium dichromate solution (3.16) required, VCr. 6.5.3 Molybdenum trioxide 6.5.3.1 Preparation of the molybdenum calibration graph NOTEThe procedures described in 6.5.3.1. and 6.5.3.2 are equivalent to the method for the determination of molybdenum in
38、BSI Handbook No. 19. Weigh and transfer seven 0.5 g portions of iron (3.12) to 250 ml conical beakers, and make additions of molybdenum solution (3.13) in accordance with Table 1. Table 1 Molybdenum calibration data Molybdenum solution (3.13)Molybdenum equivalent ml 0 2.0 4.0 6.0 8.0 10.0 12.0 mg 0
39、1.0 2.0 3.0 4.0 5.0 6.0 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.1:1992 BSI 09-19993 Treat the calibration solutions as described in 6.5.3.2 and prepare a calibration graph by plotting the absorbance reading against the m
40、illigrams of molybdenum added for each calibration solution. 6.5.3.2 Determination of molybdenum trioxide Determine molybdenum in 50 ml aliquots of the fusion filtrates (see 6.4) using the following procedure. Weigh two portions, each of 0.5 g of iron (3.12), transfer to 250 ml conical beakers, add
41、10 ml of hydrochloric acid (3.10) and heat until solvent action ceases. Oxidize with nitric acid (3.14), add 10 ml of sulfuric acid (3.18), evaporate to fuming and cool. Add a 50 ml aliquot of the test solution to one iron solution and 50 ml of the blank solution to the second iron solution. Add 10
42、ml of ammonium citrate (3.1) and neutralize with ammonia solution (3.2) adding 3 ml to 4 ml excess to dissolve any tungsten trioxide which precipitates, if necessary warming the solution. Neutralize the solution with sulfuric acid (3.18) using litmus paper as indicator and add 25 ml excess. Cool, tr
43、ansfer to a 100 ml volumetric flask and mix. Transfer a 20 ml aliquot to a 100 ml separating funnel. Make all subsequent additions of reagents using a pipette, or safety pipette as appropriate, or burette. Add 10 ml of titanium sulfate-acid mixture (3.21), 5 ml of ammonium thiocyanate (3.5), and mix
44、. Add 20 ml of n-butyl acetate (3.6), mix, add 25 ml of tin(II) chloride (3.20) and shake the funnel for approximately 30 s. Allow the two layers to separate, and discard the lower (aqueous) layer. Add 10 ml of tin(II) chloride (3.20), shake for 30 s, allow the layers to separate and again discard t
45、he lower (aqueous) layer. Dry the inside of the funnel stem with filter paper, and filter the solution through a small dry hardened filter paper, or a sintered glass crucible, porosity 4, discarding the first few millilitres of filtrate, and then fill a spectrophotometer cell (4.5). NOTEWhatman No.
46、542 grade paper has been found to be suitable. Measure the absorbance at a wavelength of 550 nm and 20 1 C. Record the absorbances of the test portion and the blank test. From the calibration graph (see 6.5.3.1) and the readings from the test portion and blank, calculate the milligrams of molybdenum
47、 in the 50 ml aliquot of the fusion filtrate (see 6.4). Multiply the results by five to obtain the total mass, MMo, of equivalent molybdenum in the tungsten trioxide. 6.5.4 Vanadium pentoxide Transfer 50 ml aliquots of the test portion and blank solution filtrates (see 6.4) to 400 ml squat beakers.
48、Add potassium dichromate solution (3.16) to the blank solution to give the same chromate concentration as that of the test portion solution. Acidify both solutions with orthophosphoric acid (3.15), add 5 ml excess, and allow to stand for 1 h. Add vanadotungstic acid solution (3.22) to the blank solu
49、tion until the colour matches that of the test portion solution. Record the volume, Vv, of vanadotungstic acid solution required. 7 Calculation and expression of results 7.1 Calculation 7.1.1 Corrections for impurities in the tungsten trioxide 7.1.1.1 Chromium trioxide The chromium trioxide correction CCr, expressed in milligrams, is given by the equation: CCr= 0.1 VCr 250/V1 7.1.1.2 Molybdenum trioxide The molybdenum trioxide correction CMo, expressed in milligrams, is given by the equation: CMo= 1.5MMo 7.1.1.3 Vanadium pentoxide The v
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