1、BRITISH STANDARD BS 6200-3.33.1: 1992 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section3.33 Determination of tungsten Subsection3.33.1 Steel: gravimetric methodBS6200-3.33.1:1992 This British Standard, having been prepared under the directionof the Iron
2、 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 comment 91/44345 DC ISBN 0 580 20801 X Committees respon
3、sible 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 (Laboratory o
4、f the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.33.1:1992 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus
5、1 5 Sampling 2 6 Procedure 2 7 Calculation and expression of results 3 8 Test report 5 Table 1 Molybdenum calibration data 2 Table 2 Precision data 4 Table 3 Values for inter-laboratory agreement(2.83 Sb, P =95%) 5 Publication(s) referred to Inside back coverBS6200-3.33.1:1992 ii BSI 09-1999 Forewor
6、d This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method1 for the determination of tungsten in BSI Handbook No.19, to which it is technically equivalent. BS6200 is a multipart British Standard, covering all aspects of th
7、e sampling and analysis of iron, steel and other ferrous 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 applicati
8、on. 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, pagesi andii, pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and ma
9、y have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6200-3.33.1:1992 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a gravimetric method for the determination of tungsten in steel. Itis suitable for steel containing3% (m/m) to30%(m
10、/m) tungsten but is not applicable to steels containing niobium and/or tantalum. 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 test portion in hydrochloric acid is oxidized to decompose carbides, then re
11、duced with sulfurous acid and the tungsten separated by hydrolysis, cinchonine being used as an auxiliary precipitant. The precipitate is ignited and weighed after removing silica by volatilization with hydrofluoric acid. Corrections are made for impurities in the tungsten trioxide. 3 Reagents Durin
12、g the analysis use only reagents of recognized analytical grade and only grade3 water as specified in BS3978. 3.1 Ammonium citrate,500g/l solution. Dissolve500g of citric acid, H 8 C 6 O 7 .H 2 O, in500ml of ammonia solution(3.2), cool, dilute to1l and mix. 3.2 Ammonia solution, density =0.91g/ml. 3
13、.3 Ammonia solution, =0.91g/ml, diluted1+1. 3.4 Ammonium nitrate,20g/l solution. Dissolve20g of ammonium nitrate in water, dilute to1l and mix. 3.5 Ammonium thiocyanate,200g/l solution. Dissolve20g of ammonium thiocyanate in70ml of water, dilute to100ml and mix. 3.6 n-Butyl acetate, in accordance wi
14、th BS551. 3.7 Cinchonine hydrochloride,100g/l solution. Dissolve10g of cinchonine hydrochloride in100ml of hydrochloric acid(3.10). 3.8 Cinchonine wash solution. Add20ml of cinchonine hydrochloride solution(3.7) and20ml of hydrochloric acid(3.9) to500ml of water, dilute to1l and mix. 3.9 Hydrochlori
15、c acid, =1.16g/ml to1.18g/ml. 3.10 Hydrochloric acid, =1.16g/ml to1.18g/ml, diluted1+1. 3.11 Hydrofluoric acid,40% (m/m). 3.12 Iron, high purity, free from molybdenum. 3.13 Molybdenum, standard solution,0.5mg of molybdenum per millilitre. Dissolve0.5g of high purity molybdenum in a mixture of10ml of
16、 sulfuric acid(3.18),5ml of nitric acid(3.14) and5ml of water. Cool, transfer to a11volumetric flask, dilute to the mark and mix. 3.14 Nitric acid, =1.42g/ml. 3.15 Orthophosphoric acid, =1.75g/ml, diluted1+1. 3.16 Potassium dichromate, standard solution, equivalent to0.1mg of chromium(III) oxide per
17、 millilitre. Dissolve0.1935g of potassium dichromate, previously dried to constant weight at150 C, in approximately500ml of water. Cool, transfer to a1lvolumetric flask, dilute to the mark and mix. 3.17 Sodium carbonate, anhydrous. 3.18 Sulfuric acid, =1.84g/ml, diluted1+1. To400ml of water, add cau
18、tiously, with cooling and stirring,500ml of sulfuric acid =1.84g/ml. Cool, dilute to1l and mix. 3.19 Sulfurous acid. In a fume cupboard, pass sulfur dioxide into1 l of water until a saturated solution is obtained. 3.20 Tin(II) chloride, 200g/l solution. Dissolve20g of tin(II) chloride, SnCl 2 .2H 2
19、O, in20ml of hydrochloric acid(3.9) and warm until a clear solution is obtained. Cool, dilute to100ml with water and mix. 3.21 Titanium sulfate-acid mixture. Dissolve1.5g of high purity titanium in a mixture of180ml of water and25ml of sulfuric acid, =1.84g/ml. To200ml of water add cautiously, while
20、 stirring,160ml of perchloric acid, =1.54g/ml, and105ml of sulfuric acid, =1.84g/ml. Cool and combine the two solutions, dilute to1 l and mix. 3.22 Vanadotungstic acid, standard solution,0.1mg of vanadium pentoxide per millilitre. Dissolve0.1286g of ammonium metavanadate,4g of tungsten trioxide and1
21、0g of sodium hydroxide in water and boil until free from ammonia. Cool, neutralize with orthophosphoric acid(3.15) and add50ml excess. Cool, transfer to a1lvolumetric flask, dilute to the mark and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with class A
22、 of BS846, BS1583 or BS1792, as appropriate. 4.3 Platinum dish 4.4 Spectrophotometer, suitable for the measurement of absorbance at a wavelength of550nm. 4.5 Cells, having an optical path length of1.0cm.BS6200-3.33.1:1992 2 BSI 09-1999 5 Sampling Carry out sampling in accordance with BS1837. NOTEBS6
23、200-2, 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. 6.2 Blank test In parallel with the determination and
24、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 a600ml squat beaker. Add60ml of hydrochloric acid(3.9), cover the beaker and heat until solvent action ceases. Evaporate to dryness and bake
25、lightly for5min. Cool, add60ml of hydrochloric acid(3.9), heat gently until the salts are dissolved and oxidize with nitric acid(3.14), added dropwise. Evaporate to approximately15ml, add30ml of hydrochloric acid(3.9) and evaporate again to approximately15ml, taking care to avoid localized drying ou
26、t of iron salts. Cool, add100ml of sulfurous acid(3.19), mix by swirling and heat to boiling. Boil for2min to3min, dilute to250ml with hot water, add a small amount of paper-pulp and5ml of cinchonine hydrochloride solution(3.7). Boil for3min, remove from the source of heat and allow to stand overnig
27、ht. 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 film of tungsten trioxide from the side of the beaker by scouring with a piece of ashless paper moistened with ammonia solution(3.3) and a
28、dd 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 exceeding800 C. Cool, moisten the residue with water, add5ml of hydrofluoric acid(3.11), and evaporate to dryness. Ignite at a temperature not exceeding
29、800 C, cool in a desiccator and weigh. Record the mass, m 1 . Mix the residue with5g of sodium carbonate(3.17) with a smooth rounded pestle and fuse at approximately1000 C for5min. Cool, extract the melt by boiling with100ml of water and simmer for1h to coagulate insoluble matter. Filter through a p
30、aper-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 hydrochloric acid(3.9), make the solution alkaline with ammonia solution(3.3) and collect the precipitate on the filter holding the insoluble matter. Reta
31、in both filter and filtrate. Transfer the filter and residue to the platinum dish(4.3), ignite at approximately800 C, cool in a desiccator and weigh. Record the mass, m 2 . Cool the fusion filtrate, transfer to a250ml volumetric flask, dilute to the mark and mix. Reserve for use for the determinatio
32、n of the oxides of chromium, molybdenum and vanadium present as impurities in the tungsten trioxide (see6.5). 6.5 Determination of chromium, molybdenum and vanadium oxides in the filtrate 6.5.1 General Determine impurities in the residue on suitable aliquots of the solution from6.4 as described in6.
33、5.2, 6.5.3 and6.5.4, using the solution from the reagent blank as the compensating blank for the chromium oxide and vanadium oxide determinations. 6.5.2 Chromium(III) oxide Transfer equal volumes(100ml or less) of the test portion and blank solution fusion filtrates (see6.4) to400ml squat beakers. A
34、dd potassium dichromate solution(3.16) to the blank solution until the colour matches that of the test portion solution. Record the volume of the aliquot used V 1and the volume of potassium dichromate solution(3.16) required, V Cr . 6.5.3 Molybdenum trioxide 6.5.3.1 Preparation of the molybdenum cal
35、ibration graph NOTEThe procedures described in6.5.3.1. and6.5.3.2 are equivalent to the method for the determination of molybdenum in BSI Handbook No.19. Weigh and transfer seven0.5g portions of iron(3.12) to250ml conical beakers, and make additions of molybdenum solution(3.13) in accordance with Ta
36、ble 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 1.0 2.0 3.0 4.0 5.0 6.0BS6200-3.33.1:1992 BSI 09-1999 3 Treat the calibration solutions as described in6.5.3.2 and prepare a calibration graph by plotting the absorbance rea
37、ding against the milligrams of molybdenum added for each calibration solution. 6.5.3.2 Determination of molybdenum trioxide Determine molybdenum in50ml aliquots of the fusion filtrates (see6.4) using the following procedure. Weigh two portions, each of0.5g of iron(3.12), transfer to250ml conical bea
38、kers, add10ml of hydrochloric acid(3.10) and heat until solvent action ceases. Oxidize with nitric acid(3.14), add10ml of sulfuric acid(3.18), evaporate to fuming and cool. Add a50ml aliquot of the test solution to one iron solution and50ml of the blank solution to the second iron solution. Add10ml
39、of ammonium citrate(3.1) and neutralize with ammonia solution(3.2) adding3ml to4ml 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 add25ml excess. Cool, transfer to a1
40、00ml volumetric flask and mix. Transfer a20ml aliquot to a100ml separating funnel. Make all subsequent additions of reagents using a pipette, or safety pipette as appropriate, or burette. Add10ml of titanium sulfate-acid mixture(3.21),5ml of ammonium thiocyanate(3.5), and mix. Add20ml of n-butyl ace
41、tate(3.6), mix, add25ml of tin(II) chloride(3.20) and shake the funnel for approximately30s. Allow the two layers to separate, and discard the lower (aqueous) layer. Add10ml of tin(II) chloride(3.20), shake for30s, allow the layers to separate and again discard the lower (aqueous) layer. Dry the ins
42、ide of the funnel stem with filter paper, and filter the solution through a small dry hardened filter paper, or a sintered glass crucible, porosity4, discarding the first few millilitres of filtrate, and then fill a spectrophotometer cell(4.5). NOTEWhatman No.542grade paper has been found to be suit
43、able. Measure the absorbance at a wavelength of550nm and20 1 C. Record the absorbances of the test portion and the blank test. From the calibration graph (see6.5.3.1) and the readings from the test portion and blank, calculate the milligrams of molybdenum in the50ml aliquot of the fusion filtrate (s
44、ee6.4). Multiply the results by five to obtain the total mass, M Mo , of equivalent molybdenum in the tungsten trioxide. 6.5.4 Vanadium pentoxide Transfer50ml aliquots of the test portion and blank solution filtrates (see6.4) to400ml squat beakers. Add potassium dichromate solution(3.16) to the blan
45、k solution to give the same chromate concentration as that of the test portion solution. Acidify both solutions with orthophosphoric acid(3.15), add5ml excess, and allow to stand for1h. Add vanadotungstic acid solution(3.22) to the blank solution until the colour matches that of the test portion sol
46、ution. Record the volume, V v , 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 C Cr , expressed in milligrams, is given by the equat
47、ion: C Cr =0.1V Cr 250/V 1 7.1.1.2 Molybdenum trioxide The molybdenum trioxide correction C Mo , expressed in milligrams, is given by the equation: C Mo =1.5M Mo 7.1.1.3 Vanadium pentoxide The vanadium pentoxide correction C v , expressed in milligrams, is given by the equation: C v =0.1 V v 5 where
48、 V Cr is the volume of potassium dichromate solution(3.16) used in6.5.2; V 1 is the volume of aliquot taken. where M Mo is the total mass of equivalent molybdenum found in6.5.3. where V v is the volume of vanadotungstic acid solution(3.22) used in6.5.4.BS6200-3.33.1:1992 4 BSI 09-1999 7.1.1.4 Total
49、correction The total correction C tot , expressed in milligrams, is given by the equation: C tot = C Cr + C Mo + C v 7.1.1.5 Corrected mass of tungsten trioxide The corrected mass of tungsten trioxide m w , expressed in grams, is given by the equation: m w = m 1 m 2 0.001C tot 7.1.2 Calculation of the tungsten content Calculate the tungsten content W, expressed as a percentage by mass, from the equation: W=0.793m w 50 7.2 Precision 7.2.1 Precision data A planned trial of this method was carried out by11 to12 analysts, each from
