1、BRITISH STANDARD BS1728-20: 1971 Method for The determination of lead in aluminium and aluminium alloys (atomic absorption method) BS1728-20:1971 This British Standard, having been approved by the Non-ferrousMetals IndustryStandards Committee,was publishedunderthe authority of the Executive Board on
2、 30 July1971 BSI11-1999 The following BSI references relate to the work on this standard: Committee reference NFE/-/3 Draft for comment70/1749 ISBN 580 06614 2 Co-operating organizations The Non-ferrous Metals Industry Standards Committee, under whose supervision this British Standard was prepared,
3、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 and Me
4、tallurgy 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 Britis
5、h 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-ferrous Met
6、als Research Non-ferrous Metal Stockists Association* Post Office Copper Development Association Royal Institute of British Architects Crown Agents for Oversea Governments Society of Motor Manufacturers and and Administrations Traders Ltd. Electric Cable Makers Confederation Tin Research Institute I
7、nstitute 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-committee entru
8、sted 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 CommentsBS1728-20:1971 BSI 11-1999 i Contents Page Co-operating
9、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 3BS1728-20:1971 ii BSI 11-1999 Foreword This standard makes reference to the following British Standard: BS1499, Sampling non-ferrous
10、metals. This method for the determination of lead is the twentieth 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 part. Other methods in the series are as follows: Par
11、t1: Copper; Part2: Magnesium; Part3: Zinc (mercuric potassium thiocyanate method); Part5: Copper (absorptiometric method); Part6: Iron (volumetric: titanous chloride method); Part8: Iron (absorptiometric1:10 phenanthroline method); Part9: Manganese (volumetric arsenite/nitrite method); Part10: Manga
12、nese (absorptiometric method); Part11: Silicon (perchloric acid method); Part12: Silicon (absorptiometric molybdenum blue method); Part13: Titanium (absorptiometric chromotropic acid method); Part14: Nickel (gravimetric method); Part15: Nickel (photometric method); Part16: Chromium (photometric meth
13、od); Part17: Chromium (volumetric method); Part18: Zinc (ion-exchangevolumetric EDTA or polarographic method); Part19: Magnesium (atomic absorption method). The preparation of this series of methods has been authorized by the Non-ferrous Metals Industry Standards Committee as part of a general progr
14、amme 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 “referee” method
15、s 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 obligations. Summary
16、 of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to3 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.BS1728-20:1971 BSI
17、11-1999 1 1 Introduction 1.1 Principle. The sample is dissolved in a mixture of nitric and hydrochloric acids and evaporated to a low volume. After filtration the solution is diluted to a suitable volume and the lead content is determined by atomic absorption spectrophotometry. 1.2 Range. The method
18、 is recommended for lead contents between0.01 and1%. 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 analysis of the results obtained. 2 Apparatus 2.1 Class A
19、volumetric glassware complying with the appropriate British Standards shall be used throughout. 2.2 Any atomic absorption spectrophotometer with adequate sensitivity and precision and preferably attached to a chart recorder readout or integrating device and capable of measuring absorption at a wavel
20、ength of283.3nm. A slot burner with air/acetylene flame. A multi-slot burner is advisable when the total solid concentration in the solutions to be aspirated exceeds0.5%. 3 Solutions required All reagents shall be of the highest purity obtainable and distilled or demineralized water shall be used th
21、roughout. Standard lead. (1mlN 0.1mg of lead.) Dissolve1.0g of high purity lead in50ml of nitric acid (50%). Boil to remove nitrous fumes, cool, transfer to a1litre volumetric flask, dilute to the mark and mix. Transfer100ml of this solution to a1litre volumetric flask, dilute to the mark and mix. T
22、his solution should be freshly prepared. Hydrochloric acid. (50%v/v.) Dilute500ml of hydrochloric acid (sp. gr. 1.161.18) to1litre and mix. Nitric acid. (50% v/v.) Dilute500ml of nitric acid (sp. gr.1.42) to1litre and mix. Nickel chloride. Dissolve0.1g of nickel in10ml of hydrochloric acid (50%). Di
23、lute to100ml and mix. 4 Sampling Recommended methods of obtaining a suitable sample for the analytical procedure given below are described in BS1499, “Sampling non-ferrous metals”. 5 Procedure 5.1 Adjust the weight of sample as follows: Leadcontent Standarddeviation % 0.009 0.049 0.19 0.63 0.74 0.00
24、19 0.0034 0.0095 0.010 0.017 Leadcontent Sampleweight % 0.01to0.1 0.1to1.0 g 1.00 0.20BS1728-20:1971 2 BSI 11-1999 5.2 Transfer the appropriate weight of sample to a250ml beaker (Note8.1) and add15ml of hydrochloric acid (sp. gr.1.161.18),5ml of nitric acid (sp. gr.1.42) and10ml of water. Cover with
25、 a watchglass and warm gently to complete the solution. 5.3 Carry out simultaneously a blank determination following the same procedure and using the same amounts of reagents as with the sample and replacing the sample by the same weight of high purity aluminium. 5.4 With the beaker covered, evapora
26、te the solution to about10ml (Note8.2) and allow to cool. Take up the residue with25ml of water and boil to complete the solution. Filter through a paper pulp pad into a250ml beaker. 5.4.1 For alloys containing up to1% of silicon. Cool the filtrate and transfer to a100ml volumetric flask, dilute to
27、the mark and mix. 5.4.2 For alloys containing more than1% of silicon. Transfer the filter pad and residue to a platinum crucible using forceps, dry and burn off the paper at as low a temperature as possible. Allow to cool, add5ml of hydrofluoric acid 1)and5drops of nitric acid (sp. gr.1.42). When th
28、e reaction has subsided, evaporate carefully to dryness (Note8.3). Dissolve the residue in5ml of nitric acid (50%) and add the solution to the main filtrate. Transfer to a100ml volumetric flask, dilute to the mark and mix. 5.5 Aspirate the solution (Note8.1) and record the values of per cent absorpt
29、ion or absorbance depending upon the instrument and type of read out. 6 Calibration 6.1 To a series of250ml beakers transfer a weight of aluminium(99.99% pure) corresponding to the sample weight and continue as in5.1 and5.2 of the procedure, adding a few drops of the nickel chloride solution to assi
30、st solution of the aluminium. 6.2 When the reaction is complete add to each, from a burette, quantities of standard lead solution(1mlN 0.1mg of lead) as shown in the following table: 6.3 Evaporate the solution to about10ml. Dilute to about25ml, heat if necessary to complete solution, then cool to ro
31、om temperature. 6.4 Transfer to a100ml volumetric flask, dilute to the mark and mix. 6.5 Aspirate the solutions (Note8.1) and record the values of per cent absorption or absorbance depending upon the instrument and type of read out. 6.6 Measure the blank (i.e.the solution containing0.00ml of lead so
32、lution) and if necessary measure the light scatter (Note8.4). Deduct the absorbance reading for the blank (Note8.5) and prepare a calibration graph by plotting absorbance values (see7 Calculation) against the nominal lead contents of the solutions. 7 Calculation If the instrument reads per cent abso
33、rption convert this to absorbance. Convert the absorbance reading for the test sample corrected for blank to percentage lead by means of the calibration graph. 1) This refers to the usual analytical reagent grade of40%w/w. Leadcontent Standardlead solution Correspondinglead in sample % 0.01to0.1 0.1
34、to1.0 ml 0,2,4,6,8,10,12 0,4,8,12,16,20,24 % 0.00,0.02,0.04,0.06, 0.08,0.10,0.12 0.00,0.20,0.40,0.60, 0.80,1.00,1.20BS1728-20:1971 BSI 11-1999 3 8 Notes 8.1 The sample solution should be prepared at the same time as the calibration standard solutions and aspirated immediately after the calibration s
35、olutions and blank without altering the instrument settings. After the last sample solution has been aspirated, it is advisable to aspirate the most concentrated standard solution once more. This is to ensure that instrument conditions have not altered (i.e.atomiser blocked etc.). 8.2 The evaporatio
36、n to low volume is to remove nitrous fumes and to minimize the effect of the acid on the burner. 8.3 If necessary repeat the treatment with hydrofluoric and nitric acids. 8.4 Light scatter in atomic absorption spectrophotometry is caused by solid particles (mainly refractories) in the flame deflecti
37、ng the light from the hollow cathode lamp resulting in a high absorbance reading. For a sample weight of 0.2g light scattering is negligible. When using a sample weight of1g the calibration blank should be corrected for light scatter as follows: 1) Note the absorbance (X) of the calibration blank so
38、lution measured at the normal wavelength of283.3nm. 2) Select a non-absorbing wavelength close to the absorbing wavelength (i.e.280.2nm) and adjust the gain control until the same baseline as for(1) is obtained. Note the absorbance (Y) measured at this wavelength. XY then gives the corrected blank (
39、Z). 8.5 When correction is made for light scatter use the corrected blank (Z).BS1728-20: 1971 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at
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