1、BRITISH STANDARD BS1728-18: 1970 Method for The determination of zinc in aluminium and aluminium alloys (Ion-exchange- volumetric EDTA or polarographic method) Methods for the analysis of aluminium and aluminium alloysBS1728-18:1970 This BritishStandard, having been approved by the Non-ferrous Metal
2、s Industry Standards Committee, waspublished under theauthorityofthe ExecutiveBoardon 12February1970 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference NFE/-/3 Draft for comment68/1376 ISBN 580 05666 X Co-operating organizations The Non-ferrous Metals In
3、dustry Standards Committee, under whose supervision this BritishStandard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Aluminium Federation* Institution of Mining and Metallurgy Association of Bronze and Brass Founder
4、s Institution of Production Engineers Association of Consulting Engineers Institution of Structural Engineers Board of Trade Lead Development Association British Bronze and Brass Ingot Light Metal Founders Association* Manufacturers Association London Metal Exchange British Electrical and Allied Man
5、ufacturers Magnesium Industry Council Association Ministry of Defence, Army Department* British Lead Manufacturers Association Ministry of Defence, Navy Department* British Non-ferrous Metals Federation National Brassfoundry Association British Non-ferrous Metals Federation Non-ferrous Metal Stockis
6、ts High Conductivity Copper Group Post Office British Non-ferrous Metals Research Royal Institute of British Architects Association* Society of British Aerospace Companies Ltd. Copper Development Association Society of Motor Manufacturers and Crown Agents for Oversea Governments and TradersLtd. Admi
7、nistrations Tin Research Institute Electric Cable Makers Confederation Zinc Development Association Institute of British Foundrymen Individual manufacturers Institute of Metals Institution of Mechanical Engineers (Automobile Division) The Government departments and scientific and industrial organiza
8、tions marked with an asterisk in the above list, together with the following, were directly represented on the sub-committee entrusted with the preparation of this BritishStandard: Association of Light Alloy Refiners and Ministry of Technology Laboratory of the Smelters Ltd. Government Chemist Indiv
9、idual analysts Amendments issued since publication Amd. No. Date CommentsBS1728-18:1970 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 2 5 Procedure 2 6 Standardization (for volumetric method) 2 7
10、 Calibration (for polarographic method) 3 8 Calculation 3 9 Notes 3BS1728-18:1970 ii BSI 12-1999 Foreword This standard makes reference to the following BritishStandard: BS1499, Sampling non-ferrous metals. BS3978, Water for laboratory use. This method for the determination of zinc is the eighteenth
11、 of a series which will form a complete BritishStandard 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: Part1: Copper; Part2: Magnesium; Part3: Zinc (mercuric potassium thioc
12、yanate method); Part4: Zinc (polarographic method); Part5: Copper (absorptiometric method); Part6: Iron (volumetric: titanous chloride method); Part7: Zinc (zinc oxide method); Part8: Iron (absorptiometric1:10 phenanthroline method); Part9: Manganese (volumetric arsenite/nitrite method); Part10: Man
13、ganese (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 me
14、thod); Part17: Chromium (volumetric method). It is intended that this method will supersede Parts4 and7 which will be withdrawn. 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
15、 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 dis
16、pute. This method is substantially the same as the corresponding method approved by ISO/TC79 which will be published as ISOR . . . 1) . 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.
17、 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, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may h
18、ave had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In course of preparation.BS1728-18:1970 BSI 12-1999 1 1 Introduction 1.1 Principle. The sample is dissolved in hydrochloric acid and zinc is separated from other elements by absorption on to
19、an anion exchange resin from a2N hydrochloric acid solution. Zinc is removed from the resin with N/200 hydrochloric acid and determined either volumetrically with EDTA or polarographically. 1.2 Range. The polarographic method is recommended for zinc contents between0.01 and0.25%, and the volumetric
20、method for zinc contents between0.10 and12.0%. 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. 1.4 Application. The volumetri
21、c method is not suitable for aluminium alloys containing cadmium. 2 Apparatus 2.1 Class A volumetric glassware complying with the appropriate BritishStandards shall be used throughout. 2.2 Anion exchange column. Glass column20mm diameter and about400mm long, fitted with a tap and filled with resin 2
22、)to a bed depth of150mm. First remove any fine particles present in the anion resin by successive washings with hydrochloric acid(N/200). Decant until a clear solution is obtained, then allow the resin to stand for several hours (preferably overnight) in hydrochloric acid (N/200). Place a little gla
23、ss wool at the bottom of the column above the tap as a support for the resin. Transfer the suspension of resin to the column to a depth of150mm, taking care to avoid the formation of air bubbles and channels. Wash the column with100ml of hydrochloric acid (N/200) at a rate of5 to7ml per minute. Cond
24、ition the exchange column by introducing, at the same rate,200ml of hydrochloric acid(2N) to which0.5ml of nitric acid (sp. gr.1.42) has been added. While the column is being prepared and during the analysis, the resin should always be covered by the liquid. 3 Solutions required All reagents shall b
25、e of the highest purity obtainable and either distilled or demineralized water complying with BS3978 3)shall be used throughout. Solutions shall be freshly prepared and where necessary filtered. Standard zinc (1mlN 2 mg of zinc). Dissolve2g of high-purity zinc in25ml of hydrochloric acid (sp. gr.1.1
26、61.18) diluted with75ml of water, transfer to a1litre volumetric flask, dilute to the mark and mix. Standard zinc (1mlN 0.02mg of zinc). Transfer10ml of standard zinc solution(1mlN 2mg of zinc) to a1litre volumetric flask, dilute to the mark and mix. EDTA (M/50).(1ml=1.3076mg of zinc.) Dissolve7.5g
27、of the disodium salt of diaminoethanetetra-acetic acid, (EDTA) in water, transfer to a1litre volumetric flask, dilute to the mark and mix. Acetic acid (6%). Dilute60ml of glacial acetic acid to1litre and mix. Ammonium acetate (50%w/v). Dissolve500g of ammonium acetate in water, dilute to1litre and m
28、ix. Base electrolyte. Dissolve125g of ammonium chloride in about400ml of water, add180ml of ammonia solution (sp. gr.0.91) and125ml of gelatin solution(2%w/v), dilute to1litre and mix. Hydrochloric acid (50%). Dilute500ml of hydrochloric acid (sp. gr.1.161.18) to1litre and mix. (2N). Dilute170ml 4)o
29、f hydrochloric acid (sp. gr.1.18) to1litre and mix. (N). Dilute85ml 4)of hydrochloric acid (sp. gr.1.18) to1litre and mix. (N/200). Dilute5ml of hydrochloric acid (N) to1litre and mix. Dithizone (0.025%w/v). Dissolve0.025g of dithizone in ethanol and dilute to100ml with ethanol. Zinc content Standar
30、d deviation % 0.1 0.4 6.0 Polarographic 0.004 0.015 Volumetric 0.005 0.009 0.022 2) A resin with23% cross-linking, e.g.Permutit Deacidite FF, (SRA62)52+100 mesh, or equivalent is suitable. 3) BS3978, “Water for laboratory use”. 4) If hydrochloric acid (sp. gr.1.16) is used these quantities should be
31、 increased by a factor of1.13.BS1728-18:1970 2 BSI 12-1999 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 Weigh2g 0.001g of sample and transfer to a400ml beaker. Add gradua
32、lly50ml of hydrochloric acid(50%). 5.2 Carry out simultaneously a blank determination following the same procedure and using the same amount of reagents as with the sample. 5.3 When the reaction appears to be complete, add hydrogen peroxide(100vol.) dropwise until any copper is completely dissolved
33、and complete the attack of the sample by heating gently. Then evaporate just to crystallization, cool and take up with100ml of hydrochloric acid(2N) and heat to facilitate solution. 5.4 Filter through a medium texture filter, previously washed with hot hydrochloric acid(50%) and then with hot water.
34、 Wash the residue and the filter with hot hydrochloric acid(2N) (about30 to50ml). 5.4.1 For zinc contents between0.01 and1.5%. Collect the filtrate and the washings in a beaker and cool to room temperature. Adjust the volume to about150ml with hydrochloric acid(2N) and add0.5ml of nitric acid (sp. g
35、r.1.42). 5.4.2 For zinc contents greater than1.5%. Collect the filtrate and the washings in a200ml volumetric flask, cool to room temperature, dilute to the mark with hydrochloric acid(2N) and mix. Take an aliquot as indicated in the table below: and transfer to a250ml beaker. Dilute to about150ml w
36、ith hydrochloric acid solution(2N) and add0.5ml of nitric acid (sp. gr.1.42). 5.5 Pass the solution through the exchange column at a rate of5 to7ml per minute. Wash the beaker and the exchange column with four successive25ml portions of hydrochloric acid(2N) followed by200ml of hydrochloric acid (N)
37、 at the rate of5 to7ml per minute. Discard the effluent. 5.6 Elute the zinc retained on the resin by passing250ml of hydrochloric acid (N/200) through the exchange column at the same rate (Note9.1). 5.7 For the volumetric method (zinc contents between0.10 and12.0%) 5.7.1 Collect the eluate in a500ml
38、 conical flask. Evaporate to70100ml and cool. Add ammonia solution (sp. gr.0.91) dropwise until the solution is neutral to litmus. 5.7.2 Add20ml of acetic acid(6%) and10ml of ammonium acetate solution(50%) (Note9.2) then add50ml of acetone and cool to about5 C. Then add2ml of dithizone indicator sol
39、ution(0.025%). 5.7.3 Titrate immediately with EDTA solution (M/50) until the colour of the indicator changes from red to orange yellow. 5.8 For the polarographic method (zinc contents between0.01 and0.25%) 5.8.1 For zinc contents between0.01 and0.05% 5.8.1.1 Collect the eluate in a400ml beaker, evap
40、orate just to dryness and dissolve in a few drops of hydrochloric acid(50%). Add20ml of the base electrolyte, transfer to a50ml volumetric flask, dilute to the mark and mix. 5.8.1.2 Remove air by passing a current of nitrogen or hydrogen through the solution. Polarograph the solution between1.0V and
41、1.5V relative to a mercury anode using a convenient sensitivity. 5.8.1.3 Read from the calibration graph (Clause7) the weight(4g) of zinc corresponding to the step heights obtained. 5.8.2 For zinc contents between0.05 and0.25% 5.8.2.1 Collect the eluate in a250ml volumetric flask (Note9.3), and remo
42、ve the flask when the level of the solution reaches within12ml of the graduation mark. Dilute to the mark with water and mix. Transfer a25ml aliquot to a50ml volumetric flask, add20ml of base electrolyte, dilute to the mark and mix. 5.8.2.2 Continue as in5.8.1.2 and5.8.1.3. 6 Standardization (for vo
43、lumetric method) 6.1 EDTA (M/50). Transfer25ml of standard zinc solution(1mlN 2mg of zinc) to a conical flask and dilute to about100ml. Add ammonia solution (sp. gr.0.91) dropwise until the solution is neutral to litmus. 6.2 Continue as in5.7.2 and5.7.3 of the procedure. Zinc content Aliquot to be t
44、aken Corresponding sample weight % 1.5 to3 3 to6 6 to8 ml 100 50 25 g 1 0.50 0.25BS1728-18:1970 BSI 12-1999 3 7 Calibration (for polarographic method) 7.1 To a series of50ml volumetric flasks, transfer aliquots(1ml to25ml) of standard zinc solution(1mlN 0.02mg of zinc) covering the range205004g of z
45、inc. Add to each20ml of the base electrolyte, dilute to the mark and mix. 7.2 Continue as in5.8.1.2 and construct a calibration graph from the step heights obtained. 8 Calculation 8.1 For the volumetric method 8.2 For the polarographic method 9 Notes 9.1 If bismuth is present in the alloy it will be
46、 retained on the column and will be seen as a light coloured band at the top of the column. It should be removed by washing the column with200ml of nitric acid(50%) followed by200ml of water. The column should then be conditioned as in2.2. 9.2 Check the pH and if necessary adjust to between5 and5.5
47、with acetic acid or ammonia solution added dropwise. 9.3 With some instruments it is necessary to increase the sensitivity by 1) evaporating to small bulk and using the whole of the solution as in 5.8.1.1, or 2) evaporating to less than100ml, transferring to a100ml volumetric flask, diluting to volu
48、me and taking a25ml aliquot. where A = volume(ml) of EDTA solution (M/50) used corrected for blank; B = volume(ml) of EDTA solution (M/50) use for standardization corrected for blank; R = ratio of volume of main solution to volume of aliquot taken; W = weight(g) of sample taken. zinc per cent A 5 R
49、WB - = where C = weight(4g) of zinc in sample corrected for blank; R = ratio of volume of main solution to volume of aliquot taken; W = weight(g) of sample taken. zinc per cent C 10 4 R W - =4 blankBS1728-18:1970 BSI 12-1999 BritishStandards The following are available on application: YEARBOOK Including subject index and numerical list of BritishStandards 1. SECTIONAL LISTS. Gratis Acoustics (SL10) Aerospace materials and components (SL25) Automobile (SL34)
