1、BRITISH STANDARD BS 1728-25: 1980 ISO 1118:1978 Methods for The analysis of aluminium and aluminium alloys Part 25: Titanium (spectrophotometric chromotropic acid method) ISO title: Aluminium and aluminium alloys Determination of titanium Spectrophotometric chromotropic acid method UDC 669.71:543.42
2、.062:546.74BS1728-25:1980 This British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee,waspublished underthe authorityof the Executive Boardand comesintoeffect on 31March1980 BSI 12-1999 The following BSI references relate to the work on this standard:
3、 Committee reference NFE/35 Draft for approval 79/71102 ISBN 0 580 11211 X Cooperating organizations The Non-ferrous Metals Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government department and scientific and industria
4、l organizations: Aluminium Federation* Association of Bronze and Brass Founders British Electrical and Allied Manufacturers Association (BEAMA) British Lead Manufacturers Association British Non-ferrous Metals Federation Copper Development Association Electric Cable Makers Confederation Institute of
5、 British Foundrymen Institution of Mechanical Engineers Institution of Mining and Metallurgy Institution of Production Engineers Institution of Structural Engineers International Tin Research Institute Lead Development Association Light Metal Founders Association* London Metal Exchange Magnesium Ind
6、ustry Council Ministry of Defence* Non-ferrous Metal Stockists* Royal Institute of British Architects* Society of Motor Manufacturers and Traders Limited* Zinc Development Association The organizations marked with an asterisk in the above list, together with the following, were directly represented
7、on the committee entrusted with the preparation of this British Standard: Association of Light Alloy Refiners Limited BNF Metals Technology Centre Bureau of Analysed Samples Limited Lloyds Register of Shipping Individual expert Amendments issued since publication Amd. No. Date of issue CommentsBS172
8、8-25:1980 BSI 12-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 2 5 Sampling 2 6 Procedure 2 7 Expression of results 5 8 Test report 5 Annex Special case of aluminium alloys in which the
9、 silicon content is greater than 1%(m/m) 6 Table 1 3 Table 2 3BS1728-25:1980 ii BSI 12-1999 National foreword This Part of BS1728 is identical with ISO1118 “Aluminium and aluminium alloys Determination of titanium Spectrophotometric chromotropic acid method” published by the International Organizati
10、on for Standardization (ISO). The method described is identical in purpose and in the range of titanium contents with those given in Part13 of BS1728. Analytical progress having rendered the latter obsolete, Part13 has now been withdrawn in favour of Part25. This method for the determination of tita
11、nium is the twenty-fifth of a series that 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: Part 1: Copper; Part 2: Magnesium; Part 5: Cop
12、per (absorptiometric method); Part 6: Iron (volumetric: titanous chloride method); Part 8: Iron (absorptiometric 1:10-phenanthroline method); Part 9: Manganese (volumetric: arsenite/nitrite method); Part 10: Manganese (absorptiometric method); Part 11: Silicon (perchloric acid method); Part 12: Sili
13、con (absorptiometric molybdenum blue method); Part 14: Nickel (gravimetric method); Part 15: Nickel (photometric method); Part 16: Chromium (photometric method); Part 17: Chromium (volumetric method); Part 18: Zinc (ion-exchange-volumetric EDTA or polarographic method); Part 19: Magnesium (atomic ab
14、sorption method); Part 20: Lead (atomic absorption method); Part 21: Zinc (atomic absorption method); Part 22: Magnesium (volumetric CDTA method); Part 23: Copper (atomic absorption method); Part 24: Nickel (atomic absorption method). The preparation of this series of methods has been directed by th
15、e Non-ferrous Metals Standards Committee as part of 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
16、be appreciated that they are primarily intended as “referee” methods to be used in cases of dispute. Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain conventions a
17、re not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Where the words “International Standard” appear,
18、referring to this standard, they should be read as “British Standard”.BS1728-25:1980 BSI 12-1999 iii 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
19、 does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 6 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated
20、in the amendment table on the inside front cover.iv blankBS1728-25:1980 BSI 12-1999 1 1 Scope and field of application This International Standard specifies a general method for the spectrophotometric determination of titanium in aluminium and aluminium alloys. The method is applicable to products h
21、aving titanium contents between0,005 and0,3% (m/m). However, the method is not applicable completely toalloys having silicon contents greater than1% (m/m), for which it must be modified as indicated in theAnnex. 2 Principle Attack of a test portion with sodium hydroxide, and acidification of the alk
22、aline solution with nitric acid and sulphuric acid. Reduction of the iron(III) with ascorbic acid, and formation of the titanium-chromotropic acid complex at a chosen pH value between2 and2,50, controlled to within 0,05pH unit. Spectrophotometric measurement of the coloured complex at a wavelength o
23、f about470nm. 3 Reagents During the analysis, use only reagents of recognized analytical grade and distilled water or water of equivalent purity. 3.1 Sodium hydroxide, 200g/l or approximately5N solution. In a nickel dish, dissolve200g of sodium hydroxide in water. After cooling, make up the volume t
24、o1000ml and mix. Immediately transfer the solution to a plastic container. 3.2 Sodium hydroxide, 80g/l or approximately2N solution. In a nickel dish, dissolve80g of sodium hydroxide in water. After cooling, make up the volume to1000ml and mix. 3.3 Nitric acid, 1,40g/ml, approximately15N solution. 3.
25、4 Sulphuric acid, 1,48g/ml, approximately18N solution. Carefully add500ml of sulphuric acid, 1,84g/ml, approximately36N solution, to approximately400ml of water. After cooling, make up the volume to1000ml and mix. 3.5 Sulphuric acid, 1,21g/ml, approximately7N solution. Carefully add200ml of sulphuri
26、c acid, 1,84g/ml, approximately36N solution, to approximately700ml of water. After cooling, make up the volume to1000ml and mix. 3.6 Sulphuric acid, 1,06g/ml, approximately2N solution. Carefully add60ml of sulphuric acid, 1,84g/ml, approximately36N solution, to approximately500ml of water. After coo
27、ling, make up the volume to1000ml and mix. 3.7 Sulphurous acid (H 2 SO 3 ), solution saturated at room temperature. 3.8 Sodium sulphite, 20g/l solution. Dissolve2g of sodium sulphite (Na 2 SO 3 ) in water and make up the volume to100ml. Prepare immediately before use. 3.9 Potassium permanganate, 1g/
28、l solution. Dissolve0,1g of potassium permanganate in water and make up the volume to100ml. 3.10 Buffer solution, pH approximately2,9. Dissolve189g of monochloroacetic acid (CH 2 ClCOOH) in approximately150ml of water and add40g of sodium hydroxide previously dissolved in approximately100ml of water
29、. Carefully mix and cool to room temperature. Filter, if necessary, through a medium texture filter paper and collect the filtrate in a500ml volumetric flask. Wash with water, make up to volume and mix. Use only a freshly prepared solution (one week maximum). 3.11 Ascorbic acid, 40g/l solution. Diss
30、olve1g of ascorbic acid in25ml of water. Prepare immediately before use. 3.12 Chromotropic acid, 20g/l solution. Dissolve2g of chromotropic acid (disodium salt of1,8-dihydroxynaphthalene-3,6-disulphonic acid) in approximately70ml of water containing0,75ml of glacial acetic acid, 1,05g/ml, approximat
31、ely18N solution. Add0,2g of sodium metabisulphite (Na 2 S 2 O 5 ) and shake until completely dissolved. Filter, if necessary, through a close texture filter paper and collect the filtrate in a100ml volumetric flask. Wash with water, make up to volume and mix. This solution should have a very slight
32、pale yellow colour and should be kept in a dark coloured container. It is stable for about three weeks. Do not use a dark coloured solution. 3.13 Mixed reagent, pH approximately0,50. Place approximately300ml of water in a1000ml volumetric flask, add250,0ml of the sodium hydroxide solution (3.1), 100
33、,0ml of the sulphuric acid solution (3.4) and18,0ml of the nitric acid solution (3.3) and mix. Cool, make up to volume and mix.BS1728-25:1980 2 BSI 12-1999 3.14 Titanium, standard solution corresponding to0,5g of Ti per litre. Prepare the solution according to one of the following methods: 3.14.1 We
34、igh, to the nearest0,00 1g, 0,50g of pure titanium (purity greater than99,5%) and place in a beaker of suitable capacity (for example, 600ml). Dissolve in125ml of the sulphuric acid solution(3.5) and oxidize with a few drops of the nitric acid solution (3.3). Boil the solution gently until all nitri
35、c acid fumes have been given off. Cool, dilute suitably, transfer, with washing, to a1000ml volumetric flask, make up to volume and mix. 1ml of this standard solution contains0,5mg of Ti. 3.14.2 Weigh, to the nearest0,000 1g, 1,848 5g of potassium titanyl oxalate dihydrate K 2 TiO(C 2 O 4 ) 2 .2H 2
36、O and place in a Kjeldahl flask of approximately100ml capacity. Add1,8g of ammonium sulphate and15ml of sulphuric acid, 1,84g/ml approximately36N solution. Heat carefully until the reaction subsides and boil gently for10min. Cool and transfer the solution, with washing, to a beaker of suitable capac
37、ity (forexample, 250ml), containing100ml of water. Add a few drops of the potassium permanganate solution (3.9) until a persistent pink colour is obtained. Transfer the solution, with washing, to a500ml volumetric flask, make up to volume and mix. 1ml of this standard solution contains0,5mg of Ti. 3
38、.15 Titanium, standard solution corresponding to0,025g of Ti per litre. Take50,0ml of the standard titanium solution(3.14), place in a1000ml volumetric flask, make up to volume and mix. 1ml of this standard solution contains0,025mg ofTi. Prepare this solution immediately before use. 3.16 Titanium, s
39、tandard solution corresponding to0,015g of Ti per litre. Take30,0ml of the standard titanium solution(3.14) and place in a1000 ml volumetric flask. Add2,0ml of the sulphuric acid solution (3.5), make up to volume and mix. 1ml of this standard solution contains0,015mg ofTi. Prepare this solution imme
40、diately before use. 3.17 Titanium, standard solution corresponding to0,0025g of Ti per litre. Take50,0ml of the standard titanium solution(3.15) and place in a500ml volumetric flask. Add2,50ml of the sulphuric acid solution(3.5), make up to volume and mix. 1ml of this standard solution contains0,002
41、5mg ofTi. Prepare this solution immediately before use. 4 Apparatus Normal laboratory apparatus, and 4.1 pH meter, having an accuracy to within at least0,02pH unit and provided with a glass electrode. 4.2 Spectrophotometer 5 Sampling 5.1 Laboratory sample 1) 5.2 Test sample Chips of thickness not mo
42、re than1mm shall be obtained by milling or drilling. 6 Procedure 6.1 Determination of the optimum pH value for the development of the colour If the colour reaction is carried out at a pH value determined exactly by experiment, the value of the absorbance for a given quantity of titanium is almost co
43、nstant. It is therefore necessary to predetermine with the particular instrument being used by operating in the pH range between2 and2,50 and by using a given quantity (forexample8,0ml) of the standard titanium solution (3.17) the interval of 0,05pH unit which ensures almost constant values of the a
44、bsorbance following the procedure specified in6.2.1, 6.2.3 and6.2.4. Subsequently, use the pH value thus found for the preparation of the calibration curve and for the determination. 1) Sampling of aluminium and aluminium alloys will be the subject of a future International Standard.BS1728-25:1980 B
45、SI 12-1999 3 6.2 Plotting of the calibration curve 6.2.1 Titanium content between 0,005 and0,03 % (m/m) 6.2.1.1 PRELIMINARY TEST FOR ADJUSTMENT OF pHVALUE Into a series of six beakers of suitable capacity (forexample, 100ml), place10,0ml of the mixed reagent solution (3.13) and add0 (compensation so
46、lution) 1,0 2,0 4,0 8,0 12,0ml respectively of the standard titanium solution(3.17). Then add, drop by drop, the potassium permanganate solution (3.9) to each beaker until a persistent pale pink colour is obtained. Eliminate the excess potassium permanganate with a slight excess of the sodium sulphi
47、te solution (3.8), add10,0ml of the buffer solution (3.10), 1,0ml of the ascorbic acid solution (3.11), 5,0ml of the chromotropic acid solution (3.12), dilute to approximately45ml and mix. Using a graduated pipette or a burette, add to each solution, while checking with the pH meter (4.1), the sodiu
48、m hydroxide solution (3.2) or the sulphuric acid solution (3.6), as applicable, while stirring, in sufficient quantity to give a pH value corresponding to the optimum determined in6.1. NOTEFor correction of the pH value, it is not absolutely necessary to use the alkaline or acid solutions in the con
49、centration specified in the method; i.e.approximately2N. More dilute or more concentrated solutions may be used, provided that the quantity of alkaline or acid solution necessary for the correction of the pH value does not exceed approximately2ml. This is in order not to increase excessively the volume of solution, bearing in mind the quantities of reagents which have to be added for development of the colour, and the final volume (50,0ml). Note the volume of sodium hydroxide or sulphuric acid
