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1、BRITISH STANDARD BS 6200-3.34.4: 1985 ISO 6467:1980 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.34 Determination of vanadium Subsection 3.34.4 Ferrovanadium: potentiometric method UDC 669.1:543.257.1:546.881 Licensed Copy: sheffieldun sheffield
2、un, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.34.4:1985 This British Standard, having been prepared under the direction of the Iron and Steel Standards Committee, was published under the authority of the Board of BSI and comes into effect on 28 February 1985 BSI 12
3、-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment 78/77992 DC ISBN 0 580 14273 6 National foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Committee. It is identical with ISO 6
4、467:1980 “Ferrovanadium Determination of vanadium content Potentiometric method” published by the International Organization for Standardization (ISO) and supersedes method 2 for the determination of vanadium in BSI Handbook No. 19. Terminology and conventions. The text of the International Standard
5、 has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain 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 i
6、t is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-reference. At present there is no corresponding British Standard for ISO 3713 which is sti
7、ll at draft stage. Appropriate procedures from ISO 3713 will be incorporated in BS 6200-2 “Methods of sampling and sample 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 res
8、ponsible for their 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 and 2, an inside back cover and a back cover. This standard has
9、 been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Unco
10、ntrolled Copy, (c) BSI BS 6200-3.34.4:1985 BSI 12-1999i Contents Page National forewordInside front cover 1Scope and field of application1 2Reference1 3Principle1 4Reagents1 5Apparatus1 6Sample2 7Procedure2 8Expression of results2 9Repeatability2 10Test report2 Publication referred toInside back cov
11、er Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.34.4:1985 BSI 12-19991 1 Scope and field of application This Int
12、ernational Standard specifies a potentiometric method for the determination of the vanadium content of ferrovanadium. The method applies to alloys having a vanadium content less than or equal to 85 % (m/m). 2 Reference ISO 3713, Ferroalloys Sampling and preparation of samples General rules1). 3 Prin
13、ciple Dissolution of a test portion with nitric and sulphuric acids. Cold oxidation of the vanadium(IV) to vanadium(V) by a slight excess of potassium permanganate. Destruction of the excess of potassium permanganate by potassium nitrite, the excess of the latter being itself destroyed by urea. Redu
14、ction of the vanadium(V) to vanadium(IV) by iron(II) in a potentiometric titration. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity, except where otherwise specified. 4.1 Urea 4.2 Nitric acid, 1,38 to 1,42 g/ml.
15、 4.3 Phosphoric acid 4.4 Sulphuric acid, 50 % (V/V) solution, rendered inert to potassium permanganate by adding a slight excess of this reagent. To 400 ml of water, add cautiously 500 ml of sulphuric acid ( approximately 1,84 g/ml); mix, cool, dilute to 1 000 ml and mix. 4.5 Potassium nitrite, 10 g
16、/l solution. Dissolve 10 g of potassium nitrite in water, dilute to 1 000 ml and mix. 4.6 Potassium permanganate, 6,3 g/l solution. Dissolve 6,3 g of potassium permanganate in water, dilute to 1 000 ml and mix. 4.7 Potassium dichromate, standard solution, c(K2Cr2O7) = 0,2 mol/l. Weigh, to the neares
17、t 0,000 5 g, exactly 9,806 4 g of potassium dichromate previously oven-dried at 105 C. Dissolve with water in a 1 000 ml volumetric flask. Dilute to the mark and mix. 4.8 Ammonium iron(II) sulphate, standard volumetric solution, cFeSO4(NH4)2SO4 . 0,2 mol/l. 4.8.1 Preparation In a 1 000 ml volumetric
18、 flask, dissolve 78,4 g of ammonium iron(II) sulphate FeSO4(NH4)2SO4.6H2O with 500 ml of warm water. When the dissolution is complete, add 100 ml of the sulphuric acid (4.4), cool, dilute to the mark and mix. 4.8.2 Standardization In a 600 ml beaker containing 280 ml of water, 10 ml of the sulphuric
19、 acid (4.4) and 10 ml of the phosphoric acid (4.3), introduce 40 ml of the potassium dichromate solution (4.7) using a burette. Titrate potentiometrically with the ammonium iron(II) sulphate solution. The end of the reaction is obtained when the maximum fall of potential is observed. This is of the
20、order of 100 mV. The correction factor C is given by the expression where V1 is the volume, in millilitres, of the ammonium iron(II) sulphate solution used. The concentration of this ammonium iron(II) solution varies, and it shall be verified for each series of determinations. 5 Apparatus Usual labo
21、ratory equipment, and in particular: 5.1 Beaker, capacity 400 ml. 5.2 Precision potentiometer 5.2.1 Electrodes Indicating electrode: platinum. Reference electrode: Hg/Hg2SO4/K2SO4 (saturated). 5.2.2 Checking of measuring system When it is not being used, the reference electrode should be immersed in
22、 a saturated potassium sulphate solution. The platinum electrode should be periodically checked with a stable redox buffer. Use, for example, a solution equionic in cerium(III) and cerium(IV) salts: 1) At present at the stage of draft. C 40 V1 - -= Licensed Copy: sheffieldun sheffieldun, na, Wed Dec
23、 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.34.4:1985 2 BSI 12-1999 Prepare this buffer by dissolving in distilled water 0,330 g of Ce(SO4)2 and 0,280 g of Ce2(SO4)3. Add sulphuric acid in order to obtain, after introduction into a 1 000 ml volumetric flask, an acidity correspo
24、nding to that of a molar solution of sulphuric acid. The response of the platinum electrode is satisfactory if, when it is coupled with the reference electrode, the milli-voltmeter shows a reading of between 710 and 740 mV. 5.3 Magnetic stirrer 6 Sample Use powder which will pass through a sieve wit
25、h a mesh size of 250 4m, prepared in accordance with ISO 3713. 7 Procedure 7.1 Test portion Take a test portion of 0,5 0,000 2 g. 7.2 Blank test Carry out a blank test, in parallel with the determination, following the same procedure and using the same reagents. 7.3 Check test Check the validity of
26、the execution of the method by carrying out, in parallel with the analysis and following the same procedure, the determination of the vanadium in one or several samples of the same type and having a known vanadium content. 7.4 Determination 7.4.1 In a 400 ml beaker, dissolve the test portion with 10
27、 ml of water, 10 ml of the nitric acid (4.2) and 50 ml of the sulphuric acid (4.4); evaporate to white sulphuric fumes then allow to cool. 7.4.2 Add 100 ml of water, poured gently down the side of the beaker and boil to dissolve the salts. Allow to cool and dilute to about 200 ml. 7.4.3 Place the be
28、aker on the magnetic stirrer, immerse the electrodes, and stir. Add the potassium permanganate solution (4.6), using a 50 ml burette, until the maximum potential is reached. Then wait 15 min. (The potential is stabilized at about 700 50 mV.) 7.4.4 Destroy the excess of potassium permanganate with th
29、e potassium nitrite solution (4.5), added dropwise every 30 s under potentiometric checking. Stop the addition when the potential reaches a value of about 200 mV. Add rapidly about 0,2 g of the urea (4.1), then 10 ml of the phosphoric acid (4.3). Wait for about 5 min for the potential to stabilize.
30、7.4.5 Titrate with the ammonium iron(II) sulphate solution (4.8), using a 50 ml burette, until the maximum fall of the potential is observed (about 100 mV). 8 Expression of results The vanadium content, expressed as a percentage by mass of the sample, is given by the formula T(V0 V2) C where Tis the
31、 constant 0,010 19; i.e. the mass of vanadium, in grams, equivalent to 1 ml of exactly 0,2 mol/l ammonium iron(II) sulphate solution; V0is the volume, in millilitres, of the ammonium iron(II) sulphate solution (4.8) used for the determination (7.4.5); V2is the volume, in millilitres, used for the bl
32、ank test (7.2); Cis the correction factor of the ammonium iron(II) sulphate solution (4.8.2); mis the mass, in grams, of the test portion (7.1). 9 Repeatability Experience has shown that the 95 % confidence limits for an experienced operator are 0,20 %. 10 Test report The test report shall include t
33、he following particulars: a) the reference of the method used; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation not included in this International Standard or regarded as optional. 100 m - - Licensed Copy: sheffieldun sheffiel
34、dun, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.34.4:1985 BSI 12-1999 Publication referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:58:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.34.4: 1985 ISO 6467:1980 BSI 389
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