BS 1728-17-1968 Methods for the analysis of aluminium and aluminium alloys - Determination of chromium (volumetric method)《铝与铝合金的分析方法 第17部分 铬的测定(容量法)》.pdf

1、BRITISH STANDARD BS1728-17: 1968 Method for The determination of chromium in aluminium and aluminium alloys (volumetric method)BS1728-17:1968 This British Standard, having been approved by the Non-ferrousMetals Industry Standards Committee, was published under the authority ofthe Executive Board on

2、31 December1968 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference NFE/-/3 Draft for comment 67/13649 ISBN 580 00410 4 Co-operating organizations The Non-ferrous Metals Industry Standards Committee, under whose supervision this British Standard was prep

3、ared, consists of representatives from the following Government departments, and scientific and industrial organizations: Aluminium Federation* Institution of Mechanical Engineers Association of Bronze and Brass Founders (Automobile Division) Association of Consulting Engineers Institution of Mining

4、 and Metallurgy Board of Trade Institution of Production Engineers British Bronze and Brass Ingot Institution of Structural Engineers Manufacturers Association Lead Development Association British Electrical and Allied Manufacturers Light Metal Founders Association* Association London Metal Exchange

5、 British Lead Manufacturers Association Magnesium Industry Council British Non-ferrous Metals Federation Ministry of Defence, Army Department* British Non-ferrous Metals Federation Ministry of Defence, Navy Department* High Conductivity Copper Group National Brassfoundry Association British Non-ferr

6、ous Metals Research Non-ferrous Metal Stockists Association* Post Office Copper Development Association Royal Institute of British Architects Crown Agents for Oversea Governments and Society of Motor Manufacturers and Traders Administrations Ltd. Electric Cable Makers Confederation Tin Research Inst

7、itute Institute of British Foundrymen Zinc Development Association Institute of Metals Individual manufacturers The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the sub-committe

8、e entrusted with the preparation of this British Standard: Association of Light Alloy Refiners and Individual analysts Smelters Ltd. Ministry of Technology Laboratory of the Government Chemist Amendments issued since publication Amd. No. Date CommentsBS1728-17:1968 BSI 11-1999 i Contents Page Co-ope

9、rating organizations Inside front cover Foreword ii 1 Introduction 1 2 Apparatus 1 3 Solutions required 1 4 Sampling 1 5 Procedure 1 6 Standardization 1 7 Calculation 2 8 Notes 2BS1728-17:1968 ii BSI 11-1999 Foreword This standard makes reference to the following British Standard: BS 1499, Sampling

10、non-ferrous metals. BS 3978, Water for laboratory use. This method for the determination of chromium is the seventeenth of a series which will form a complete British Standard under the collective title “Methods for the analysis of aluminium and aluminium alloys”, each being published as a separate

11、part. Other methods in the series are as follows: Part1: Copper; Part2: Magnesium; Part3: Zinc (mercuric potassium thiocyanate method); Part4: Zinc (polarographic method); Part5: Copper (absorptiometric method); Part6: Iron (volumetric: titanous chloride method); Part7: Zinc (zinc oxide method); Par

12、t8: Iron (absorptiometric1:10-phenanthroline method); Part9: Manganese (volumetric: arsenite/nitrite method); Part10: Manganese (absorptiometric method); Part11: Silicon (perchloric acid method); Part12: Silicon (absorptiometric molybdenum blue method); Part13: Titanium (absorptiometric chromotropic

13、 acid method); Part14: Nickel (gravimetric method); Part15: Nickel (photometric method); Part16: Chromium (photometric method). The preparation of this series of methods has been authorized by the Non-ferrous Metals Industry Standards Committee as part of a general programme for the standardization

14、of methods for the sampling and analysis of non-ferrous metals. The methods have been found to give reliable and reproducible results and, while in some instances they may appear to be lengthy, it should be appreciated that they are primarily intended as “referee” methods to be used in cases of disp

15、ute. 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. Summary of pages This document compr

16、ises a front cover, an inside front cover, pagesi andii, pages1 and2 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 front cover.BS1728-17:1968 BSI 11-1999 1 1 Introduction 1.1

17、 Principle. The alloy is dissolved in sodium hydroxide solution, the solution is acidified, then oxidized with ammonium persulphate in the presence of silver nitrate. Permanganic acid is reduced with sodium nitrite and the chromium is titrated with ammonium ferrous sulphate. 1.2 Range. The method is

18、 recommended for chromium contents between0.05 and0.5%. 1.3 Reproducibility. Experiments have been carried out independently by a number of analysts using this method. The degree of reproducibility that can be expected is shown by the following results obtained: 2 Apparatus Class A volumetric glassw

19、are complying with the relevant British Standards shall be used throughout. 3 Solutions required All reagents shall be of the highest purity obtainable and either distilled or demineralized water complying with BS3978 1)shall be used throughout. Standard potassium dichromate (N/40). Dissolve1.2259g

20、of potassium dichromate (previously dried to constant weight at150 C) in about500ml of water. Cool, transfer to a1litre volumetric flask, dilute to the mark and mix. Ammonium ferrous sulphate (N/40 approx.) Dissolve9.8g of ammonium ferrous sulphate (NH 4 ) 2 SO 4 .FeSO 4 .6H 2 O) in a mixture of50ml

21、 of water and50ml of sulphuric acid (sp. gr.1.84) and cool. Transfer to a1litre volumetric flask, dilute to the mark and mix. Silver nitrate (1%w/v). Dissolve10g of silver nitrate in water, dilute to1litre and mix. Sodium hydroxide (20%w/v). Dissolve200g of sodium hydroxide in water, dilute to1litre

22、 and mix. Sodium nitrite (0.3%w/v). Dissolve0.3g of sodium nitrite in water, dilute to100ml and mix. Preoxidized sodium diphenylamine sulphonate. It is recommended that pellets containing the equivalent of1mg of preoxidized sodium diphenylamine sulphonate should be used. Alternatively, the following

23、 solution may be used: Barium diphenylamine sulphonate (0.2% w/v). Dissolve0.2g of barium diphenylamine sulphonate in water, dilute to100ml and allow to stand overnight. 4 Sampling Recommended methods of obtaining a suitable sample for the analytical procedure given below are described in BS1499, “S

24、ampling non-ferrous metals”. 5 Procedure 5.1 Weigh2g of sample and transfer to a600ml tall form beaker marked at225ml. Add50ml of sodium hydroxide solution(20%). 5.2 Simultaneously carry a blank determination through the procedure using the same quantities of reagents. 5.3 When the reaction has subs

25、ided warm to complete the solution of the sample. 5.4 Add100ml of the acid mixture and bring to the boil. Add25ml of silver nitrate solution(1%) and2.5g of ammonium persulphate and boil for10minutes. 5.5 Remove from the source of heat and dilute to225ml with cold water. Reduce any permanganic acid i

26、n the warm solution by dropwise addition of sodium nitrite solution(0.3%) and add not more than5 drops in excess. Immediately add1.4g of urea and stir until dissolved. Allow to stand for2minutes, then cool to room temperature. 5.6 Add one pellet of preoxidized sodium diphenylamine sulphonate or1ml o

27、f barium diphenylamine sulphonate solution(0.2%) and titrate with ammonium ferrous sulphate solution (N/40approx.) until one drop discharges the violet colour (Note8.1). 6 Standardization 6.1 Transfer25ml of the acid mixture to a600ml beaker and dilute to200ml. Chromium content Standard deviation %

28、0.06 0.25 0.36 % 0.0037 0.0030 0.0063 1) BS3978, “Water for laboratory use”. Acid mixture: orthophosphoric acid (sp. gr.1.75) sulphuric acid (sp. gr.1.84) nitric acid (sp. gr.1.42) water 500ml 250ml 200ml 1550mlBS1728-17:1968 2 BSI 11-1999 6.2 Add25ml of potassium dichromate solution (N/40), one pel

29、let of preoxidized sodium diphenylamine sulphonate or1ml of barium diphenylamine sulphonate solution(0.2%) and titrate with ammonium ferrous sulphate solution (N/40approx.) until one drop discharges the deep violet colour. 7 Calculation 1ml ofN/40 solution=0.4334mg of chromium Chromium per cent= 8 N

30、otes 8.1 If the sample contains vanadium this should be determined separately and a deduction made on the following basis: Vanadium per cent 0.34=Chromium per cent where A = volume (ml) of ammonium ferrous sulphate solution used, calculated in terms of a N/40 solution; W = weight (g) of sample taken

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