1、BRITISH STANDARD BS 6200-3.33.3: 1985 ISO7693:1984 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section3.33 Determination of tungsten Subsection3.33.3 Ferrotungsten: gravimetric method ISO title: Ferrotungsten Determination of tungsten content Cinchonine g
2、ravimetric method UDC 669.1:543.21:546.78BS6200-3.33.3:1985 This British Standard, having been prepared under the directionof the Iron and SteelStandards Committee, waspublished under the authorityof the Board of BSIandcomes into effect on 28 February1985 BSI10-1999 The following BSI references rela
3、te to the work on this standard: Committee reference ISM/18 Draft for comment82/74267 DC ISBN 0 580 14272 8 National foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Committee. It is identical with ISO7693:1984 “Ferrotungsten Determination of t
4、ungsten content Cinchonine gravimetric method” published by the International Organization for Standardization (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 certai
5、n conventions are not identical with those used in British Standards; attention is drawn especially to the 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
6、Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-reference. At present there is no corresponding British Standard for ISO3713 which is still at draft stage. Appropriate procedures from ISO3713 will be incorporated in BS6200-2 “Methods of sampling and sam
7、ple preparation”, which will be published in due course. 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 leg
8、al 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 indicated in the amendment table
9、on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS6200-3.33.3:1985 BSI 10-1999 i Contents Page National foreword Inside front cover 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Sample 2 7 Procedure 2 8 Expre
10、ssion of results 3 9 Test report 3 Annex A Determination of molybdenum 4 Publication referred to Inside back coverii blankBS6200-3.33.3:1985 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a cinchonine gravimetric method for the determination of the tungsten cont
11、ent of ferrotungsten. It also specifies, in the annex, a spectrometric method for the determination of molybdenum which interferes with the determination. The method is applicable to ferrotungsten having tungsten contents between70and90% (m/m). 2 Reference ISO3713, Ferroalloys Sampling and preparati
12、on of samples General rules 1) . 3 Principle Dissolution of a test portion using hydrofluoric, nitric and sulphuric acids. Evaporation of the solution until copious white fumes are evolved. Separation and fusion of the residue with sodium carbonate and diboron trioxide. Dissolution of the fused resi
13、due in hot water. Precipitation of the tungsten with cinchonine and -benzoin oxime, ignition of the precipitate and weighing of the impure tungstic oxide. Purification of the impure tungstic oxide by fusion with sodium carbonate, dissolution in hot water, filtration and recovery of the insoluble imp
14、urities. Spectrometric determination of molybdenum (seethe Annex A). Determination of the tungsten content from the difference between the mass of the impure tungstic oxide and that of the impurities. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical
15、 grade and only distilled water or water of equivalent purity. 4.1 Sodium carbonate 4.2 Acetone 4.3 Diammonium hydrogen citrate (NH 4 ) 2 HC 6 H 5 O 7 4.4 Diboron trioxide (B 2 O 3 ) 4.5 Nitric acid, 1,40g/ml, approximately14mol/l solution. 4.6 Hydrofluoric acid, 1,16g/ml, approximately48% (m/m) sol
16、ution. 4.7 Hydrochloric acid, 1,19g/ml, approximately12mol/l solution. 4.8 Ethanol, approximately0,790g/ml. 4.9 Sulphuric acid, diluted1+1. Carefully add1volume of sulphuric acid ( 1,84g/ml, approximately18mol/l solution) to1volume of water and mix thoroughly whilst cooling. 4.10 Hydrochloric acid,
17、diluted1+9. Add1volume of the hydrochloric acid(4.7) to9volumes of water and mix thoroughly. 4.11 Hydrochloric acid, diluted1+99. Add1volume of the hydrochloric acid(4.7) to99volumes of water and mix thoroughly. 4.12 Ammonium hydroxide, diluted1+1. Add1volume of ammonium hydroxide 0,885g/ml, approxi
18、mately32% (m/m) solution to1 volume of water and mix thoroughly. 4.13 Ammonium chloride,20g/l solution. Dissolve2g of ammonium chloride in water, dilute to100ml and mix thoroughly. 4.14 Cinchonine,125g/l solution. Dissolve125g of cinchonine in hydrochloric acid(4.7) diluted1+1, and complete to1000ml
19、 with that acid. 4.15 -benzoin oxime,30g/l solution. Dissolve3g of -benzoin oxime in95ml of acetone(4.2). Transfer to a100ml one-mark volumetric flask, dilute to the mark with water and mix thoroughly. 4.16 Cinchonine/ -benzoin oxime, wash solution. Place10ml of the cinchonine solution(4.14),5ml of
20、the -benzoin oxime solution(4.15) and2,5ml of the hydrochloric acid(4.7) in a1000ml one-mark volumetric flask, dilute to the mark with water and mix thoroughly. 4.17 Ammonium thiocyanate,100g/l solution. Dissolve100g of ammonium thiocyanate in water, dilute to1000ml and mix thoroughly. 4.18 Tin (II)
21、 chloride,200g/l solution in hydrochloric acid(4.7) diluted1+1. Dissolve40g of tin (II) chloride dihydrate (SnCl 2 2H 2 O) in150ml of hydrochloric acid(4.7) diluted1+1. Heat gently, cool, dilute to200ml with more of the hydrochloric acid diluted1+1 and mix thoroughly. Prepare this solution immediate
22、ly before use. 4.19 Phenolphthalein,1g/l solution in the ethanol(4.8) solution. 1) At present at the stage of draft.BS6200-3.33.3:1985 2 BSI 10-1999 5 Apparatus Usual laboratory equipment and in particular. 5.1 Spectrophotometer 2) , with selector for continuous variation of wavelength, or 5.2 Spect
23、rometer 2) , with selector for discontinuous variation of wavelength, equipped with appropriate filters giving maximum transmission at a wavelength of460nm. 5.3 Cells 2) , of thickness1 (or2) cm. 6 Sample Use powder which will pass through a sieve of aperture size1604m, prepared in accordance with I
24、SO3713. 7 Procedure 7.1 Test portion Take a test portion of1 0,001g. 7.2 Blank test Carry out a blank test in parallel with the determination, following the same procedure and using the same quantities of all the reagents, but omitting the test portion. 7.3 Control test Check the validity of the ope
25、rating procedures used by carrying out, in parallel with the determination and following the same procedure, determination(s) of the tungsten content(s) of one or several samples of the same type, having known tungsten content(s). 7.4 Determination 7.4.1 Dissolution Place the test portion in a60ml p
26、latinum crucible fitted with a platinum lid and add5ml of the hydrofluoric acid(4.6). Add the nitric acid(4.5) carefully, drop by drop, and heat to light boiling until decomposition of the test portion is complete. Remove from the source of heat and rinse the sides of the crucible and the lid with w
27、ater. Add15ml of the sulphuric acid solution(4.9) and heat carefully on a sand-bath until copious white fumes are evolved. Allow to cool, and then dissolve the soluble salts in10ml of the hydrochloric acid(4.7) and30ml of hot water. 7.4.2 Filtration of impure tungstic oxide Filter the contents of th
28、e60ml platinum crucible on a fine-grained ashless filter paper, collecting the filtrate in a600ml beaker. Wash the filter and the precipitate with the hydrochloric acid solution(4.10). Dissolve the precipitate (essentially tungstic acid) in the smallest possible quantity of ammonium hydroxide soluti
29、on(4.12), then wash the filter with the ammonium chloride solution(4.13). Collect the solution resulting from dissolution and washing with the filtrate in the600ml beaker. 7.4.3 Treatment of any insoluble residue remaining on the filter Transfer the filter with any insoluble residue to the original6
30、0ml platinum crucible. Dry and ignite the filter, heating the residue at a temperature below750 C. Cool, add0,5g of the sodium carbonate(4.1) and0,5g of the diboron trioxide(4.4). Heat over a burner, gently at first, and then more strongly, until the mixture just fuses. Cool, and then dissolve the f
31、used material in hot water. Filter the solution obtained on a fine-grained filter paper, collecting the filtrate in the same600ml beaker (see7.4.2). Wash the filter with hot water. 7.4.4 Precipitation of tungsten 7.4.4.1 Acidify the solution in the600ml beaker by adding10ml in excess of the hydrochl
32、oric acid(4.7). Boil for5min. Remove the beaker from the source of heat and dilute the contents to approximately450ml with hot water. Add30ml of the cinchonine solution(4.14) and a small amount of ashless filter paper pulp, and allow the solution to stand for30min at90 C, agitating it from time to t
33、ime. Then allow the solution to stand at ambient temperature for at least4h or, preferably, overnight. 7.4.4.2 Add5ml of the -benzoin oxime solution(4.15) and agitate vigorously for a few minutes. Allow to stand for1h at ambient temperature. Filter using a conical filter funnel with an11cm diameter
34、filter paper containing a little ashless filter paper pulp. Wash three times by decantation, then with the hot cinchonine/ -benzoin oxime solution(4.16) and then several times with cold hydrochloric acid solution(4.11). Finally wash with cold water. 2) These are required for the determination of mol
35、ybdenum (seethe Annex A) when the molybdenum content of the sample is not known.BS6200-3.33.3:1985 BSI 10-1999 3 Transfer the filter containing the precipitate to a tared platinum crucible and heat carefully to complete incineration. Add a few drops of the nitric acid(4.5) and evaporate to dryness o
36、n a sand-bath. Ignite the tungstic oxide (for approximately30min) at a temperature not exceeding750 C 3)in an electric muffle furnace until constant mass is attained. Allow to cool in a desiccator and weigh the crucible containing the impure tungstic oxide. 7.4.4.3 Add5g of the sodium carbonate(4.1)
37、 and mix completely with the impure tungstic oxide. Cover the mixture with1 to2g of the sodium carbonate(4.1) and heat the mixture until it fuses. Swirl the crucible to detach the tungstic oxide adhering to the walls of the crucible to incorporate it with the fused mass. Cool, and dissolve the fused
38、 material in hot water. Add some drops of the ethanol(4.8), heat for a few minutes, filter and wash the crucible and residue with hot water, retaining the filtrate (filtrate A). Transfer the filter containing the residue, to the crucible and ignite; add1 to2g of the sodium carbonate(4.11) and again
39、fuse. Dissolve the fused mass in water, add some drops of the ethanol(4.8), filter and wash the residue thoroughly to remove the sodium carbonate completely (filtrate B). Combine filtrate A with filtrate B in order to determine the molybdenum content (seethe Annex A) if required. Place the filter co
40、ntaining the residue in the crucible, ignite, at a temperature not exceeding750 C in the electric muffle furnace. Allow to cool and weigh. 8 Expression of results The tungsten content, expressed as percentage by mass, is given by the formula where m 0 is the mass, in grams, of the test portion; m 1
41、is the mass in grams, of the impure tungstic oxide (see7.4.4.2); m 2 is the mass, in grams, of the residue obtained after fusion with sodium carbonate (see7.4.4.3); m 3 is the mass, in grams, of the impure tungstic oxide in the blank test (see7.2); m 4 is the mass, in grams, of the residue obtained
42、after fusion with sodium carbonate in the blank test (see7.2); 0,7930 is the conversion factor to express the tungstic oxide content as the tungsten content. 9 Test report The test report shall include the following information: a) a reference to this International Standard; b) identification of the
43、 sample; c) the result and the method of expression used; d) any unusual features noted during the determination; e) details of any operations not specified in this International Standard or regarded as optional. 3) The temperature of750 C should not be exceeded, because, at a temperature even sligh
44、tly higher than this, tungstic oxide volatilizes slowly and continuously and this may lead to appreciable errors.0,793 0 m 1 m 2 ()m 3 m 4 () m 0 -100 BS6200-3.33.3:1985 4 BSI 10-1999 Annex A Determination of molybdenum A.1 General The tungstic oxide obtained may contain traces (some hundredths of1%
45、) of molybdenum in the form of molybdic oxide. If the molybdenum content is not known, it is necessary to determine it spectrometrically and to correct the mass of tungstic oxide. A.2 Procedure Boil the combined filtrate (A+B) to concentrate the solution to a volume of approximately80ml. Transfer th
46、e solution to a100ml one-mark volumetric flask, dilute to the mark with water and mix thoroughly. Transfer a10ml aliquot portion of this solution, containing not more than0,30mg of molybdenum, to a50ml one-mark volumetric flask. Add2g of the diammonium hydrogen citrate(4.3) and agitate until dissolu
47、tion is complete. Add3drops of the phenolphthalein solution(4.19), the hydrochloric acid(4.7) until the red coloration is eliminated, and then5ml of the hydrochloric acid in excess. Add, agitating after each addition,5ml of the ammonium thiocyanate solution(4.17),20ml of the acetone(4.2) and7ml of t
48、he tin (II) chloride solution(4.18). Dilute to the mark with acetone and mix thoroughly. Carry out the spectrometric measurements on the solution, using the spectrometer(5.1) set a wavelength of approximately460nm, or the spectrometer(5.2) equipped with the appropriate filters. (Cells of thickness1c
49、m are generally used.) Carry out the measurements within a period not exceeding15min after coloration. Determine the molybdenum content from the calibration graph and (see clauseA.3) and subtract the mass of molybdic oxide thus obtained from the mass of the impure tungstic oxide. A.3 Preparation of the calibration graph Prepare standard matching solutions by placing varying amounts of standard molybdenum solutions (corresponding to
