1、BRITISH STANDARD BS1728-16: 1968 Method for The determination of chromium in aluminium and aluminium alloys (Photometric method) Methods for the analysis of aluminium and aluminium alloysBS1728-16:1968 This BritishStandard, having been approved by the Non-ferrous Metals Industry Standards Committee,
2、 was published under the authority ofthe Executive Board on 31December1968 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference NFE/-/3 Draft for comment67/13648 ISBN 0 580 00408 2 Co-operating organizations The Non-ferrous Metals Industry Standards Commit
3、tee, under whose supervision this BritishStandard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Aluminium Federation* Association of Bronze and Brass Founders Association of Consulting Engineers Board of Trade British
4、 Bronze and Brass Ingot Manufacturers Association British Electrical and Allied Manufacturers Association British Lead Manufacturers Association British Non-ferrous Metals Federation British Non-ferrous Metals Federation High Conductivity Copper Group British Non-ferrous Metals Research Association*
5、 Copper Development Association Crown Agents for Oversea Governments and Administrations Electric Cable Makers Confederation Institute of British Foundrymen Institute of Metals Institution of Mechanical Engineers (Automobile Division) Institution of Mining and Metallurgy Institution of Production En
6、gineers Institution of Structural Engineers Lead Development Association Light Metal Founders Association* London Metal Exchange Magnesium Industry Council Ministry of Defence, Army Department* Ministry of Defence, Navy Department* National Brassfoundry Association Non-ferrous Metal Stockists Post O
7、ffice Royal Institute of British Architects Society of Motor Manufacturers and Traders Ltd. Tin Research Institute Zinc Development Association Individual manufacturers The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the
8、 following, were directly represented on the sub-committee entrusted with the preparation of this BritishStandard: Association of Light Alloy Refiners and Smelters Ltd. Ministry of TechnologyLaboratory of the Government Chemist Individual analysts Amendments issued since publication Amd. No. Date Co
9、mmentsBS1728-16:1968 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Introduction 1 2 Apparatus 1 3 Solutions required 1 4 Sampling 1 5 Procedure 1 6 Calibration 2 7 Calculation 2 8 Notes 2BS1728-16:1968 ii BSI 12-1999 Foreword This standard makes reference to
10、 the following British Standard: BS1499, Sampling non-ferrous metals. BS3978, Water for laboratory use. This method for the determination of chromium is the sixteenth of a series which will form a complete BritishStandard under the collective title “Methods for the analysis of aluminium and aluminiu
11、m alloys”, each being published as a separate 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
12、 method); Part7: Zinc (zinc oxide method); Part8: 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);
13、Part13: Titanium (absorptiometric chromotropic acid method); Part14: Nickel (gravimetric method); Part15: Nickel (photometric method); Part17: Chromium (volumetric method). The preparation of this series of methods has been authorized by the Non-ferrous Metals Industry Standards Committee as part of
14、 a general programme for the standardization 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
15、“referee” methods to be used in cases of dispute. 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 obli
16、gations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and 2 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.B
17、S1728-16:1968 BSI 12-1999 1 1 Introduction 1.1 Principle. The alloy is dissolved in sodium hydroxide solution, the solution is acidified, oxidized with potassium permanganate, and diphenylcarbazide solution is added to develop the colour. The optical density of the solution is then measured at about
18、540nm. 1.2 Range. The method is recommended for chromium contents between0.01 and0.1%. 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 Appa
19、ratus 2.1 Class A volumetric glassware complying with the relevant BritishStandards shall be used throughout. 2.2 Any instrument suitable for measuring the optical density of the solution at a wavelength of540nm may be used together with2 or1cm cells. Alternatively, when a filter photometer with two
20、 balanced photo-cells is used, the following conditions have been found suitable: Mercury vapour lamp; Ilford605or equivalent filter; 2 or1cm cells. 3 Solutions required All reagents shall be of the highest purity obtainable and either distilled or demineralized water complying with BS3978 1)shall b
21、e used throughout. Standard chromium (1.0mlN 0.010mg of chromium). Dissolve2.8290g of potassium dichromate (previously dried to constant weight at150 C) in water, acidify with5ml of sulphuric acid(50%) and add sulphurous acid in excess. Boil for15minutes to remove excess of sulphur dioxide, cool, tr
22、ansfer to a1litre volumetric flask, dilute to the mark and mix. Transfer10ml of this solution to a1litre volumetric flask, dilute to the mark and mix. Diphenylcarbazide (0.1%w/v). Dissolve0.10g of1,5-diphenylcarbazide (Note8.1) in5ml of glacial acetic acid, dilute to100ml and mix. This solution shou
23、ld be freshly prepared. Ammonium ferric sulphate (0.43%w/v). Dissolve4.3g of ammonium ferric sulphate (NH 4 ) 2 SO 4 .Fe 2 (SO 4 ) 3 .24H 2 O in water, add5ml of sulphuric acid(50%), dilute to1litre and mix. Phosphoric acid (10%v/v). Dilute100ml of orthophosphoric acid (sp. gr.1.75) to1litre and mix
24、. Potassium permanganate (0.3%w/v). Dissolve0.3g of potassium permanganate in water, dilute to100ml and mix. Sodium hydroxide (20%w/v). Dissolve200g of sodium hydroxide in water, dilute to1litre and mix. Sulphuric acid (50%v/v). To400ml of water add cautiously500ml of sulphuric acid (sp. gr.1.84). M
25、ix, cool, dilute to1litre and mix. Sulphurous acid. Pass sulphur dioxide gas into1litre of water until a saturated solution is obtained. 4 Sampling Recommended methods for obtaining a suitable sample for the analytical procedure given below are described in BS1499, “Sampling non-ferrous metals”. 5 P
26、rocedure 5.1 Weigh0.10g of sample and transfer to a150ml squat beaker. Add2ml of sodium hydroxide solution(20%). 5.2 Simultaneously carry a blank determination through the procedure using the same quantities of reagents. 5.3 When solution is complete, add1ml of ammonium ferric sulphate solution(0.43
27、%), dilute to10ml and boil for12 minutes. Add3ml of sulphuric acid(50%),1ml of phosphoric acid(10%) and3drops of nitric acid (sp. gr.1.42) and warm to complete solution. Filter through a hardened paper 2)if necessary. Chromium content Standard deviation % 0.026 0.046 0.109 % 0.0020 0.0030 0.0038 1)
28、BS3978, “Water for laboratory use”. 2) Whatman No.540 is suitable.BS1728-16:1968 2 BSI 12-1999 5.4 Cool, dilute to40ml, add1ml of potassium permanganate solution(0.3%) and boil for5minutes. Dilute to60ml with hot water, add2.0ml of hydrochloric acid (sp. gr.1.161.18), then boil for5minutes. 5.5 Cool
29、 (Note8.2), transfer to a100ml volumetric flask, dilute to about90ml, then add10ml of diphenylcarbazide solution(0.1%), dilute to the mark and mix. 5.6 Measure the optical density within5minutes using the conditions specified under “Apparatus”. For chromium contents up to0.05% use a2cm cell and for
30、higher contents use a1cm cell. 6 Calibration 6.1 Into a series of150ml squat beakers, transfer amounts of standard chromium solution(1mlN 0.010mg of chromium) to cover the range00.08mg of chromium(2cm cell) or00.16mg of chromium(1cm cell). Continue from5.3 of the Procedure. 6.2 Deduct the blank on t
31、he reagents from the gross optical density and prepare a calibration graph by plotting the net values against the nominal chromium contents of the solutions. 7 Calculation Convert the optical density readings for the test sample to percentage chromium by means of the calibration graph. 8 Notes 8.1 T
32、he reagent should be pinkish in colour and any material which is buff in colour should not be used. The most satisfactory criterion of the quality of the reagent is its melting point which should be between175 and177 C. 8.2 If cloudy, filter the solution.blankBS1728-16: 1968 BSI 389 Chiswick High Ro
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