1、BRITISH STANDARD BS 6200-3.1.2: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.1 Determination of aluminium Subsection 3.1.2 Steel and cast iron: spectrophotometric methodBS6200-3.1.2:1991 This British Standard, having been prepared under the
2、 directionof the Iron and SteelStandards Policy Committee, was published underthe authority of the Standards Board and comes into effect on 20December1991 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment91/38340 DC ISBN 0 580
3、20226 7 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/18, upon which the following bodies were represented: BCIRA British Steel Industry Department of Trade a
4、nd Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.1.2:1991 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3
5、 Reagents 1 4 Apparatus 2 5 Sampling 2 6 Procedure 2 7 Calculation and expression of results 4 8 Test report 5 Figure 1 Cell for electrolysis with mercury cathode 3 Table 1 Aliquot data 4 Table 2 Calibration data 4 Table 3 Precision data 5 Table 4 Predicted values of r and R 5 Publication(s) referre
6、d to Inside back coverBS6200-3.1.2:1991 ii BSI 09-1999 Foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method3 for the determination of aluminium in BSI Handbook No.19, to which it is technically equivalent. BS
7、6200 is a multipart British Standard, covering all aspects of the sampling and analysis of iron, steel and other ferrous metals. A list of contents, together with general information, is given in Part1. A British Standard does not purport to include all the necessary provisions of a contract. Users
8、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 comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, an inside back cover and a bac
9、k 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.BS6200-3.1.2:1991 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a spectrophotometric method for the determination
10、 of aluminium in steel and cast iron. The method is applicable to aluminium contents from0.001% (m/m) to0.10% (m/m). It is unsuitable for steels containing beryllium. NOTEThe titles of the publications referred to in this Subsection of BS6200 are listed on the inside back cover. 2 Principle After di
11、ssolving the test portion in acid, any insoluble residue is fused with sodium hydrogen sulfate and the extract is combined with the main solution. Interfering elements are removed by mercury cathode electrolysis followed by sodium hydroxide separation. Aluminium is converted into its eriochromecyani
12、ne complex, and the determination is completed spectrophotometrically. 3 Reagents NOTEIt is essential to store all reagent solutions in stoppered polyethylene bottles. During the analysis use only reagents of recognized analytical grade, known to give a very low aluminium blank, and only grade3 wate
13、r as specified in BS3978. 3.1 Aluminium standard solution, 0.1mg aluminium per millilitre. Dissolve1.7584g of aluminium potassium sulfate, Al 2 (SO 4 ) 3 .K 2 SO 4 .24H 2 O, in water. Transfer to a 1L volumetric flask, dilute to the mark and mix. 3.2 Acetate buffer. Dissolve 92g of ammonium acetate
14、and37g of sodium acetate, CH 3 COONa.3H 2 O, in water, add4mL of acetic acid(3.3), dilute to1L and mix. Adjust the pH to6.10 0.05 with acetic acid (3.3) or sodium hydroxide solution (3.19). 3.3 Acetic acid, density = 1.049g/mL. 3.4 Acetone 3.5 Calcium oxide 3.6 Eriochromecyanine, 1g/L solution. Diss
15、olve0.1g of eriochromecyanine in water, dilute to100mL and mix. Prepare this solution freshly for each batch of tests, allow to stand for1h, and then use without delay. NOTEAlso known as Eriochromecyanine R; Solochromecyanine R; CI43820. Supplies of this reagent may vary in colour. 3.7 Hydrochloric
16、acid, = 1.16g/mL to1.18g/mL. 3.8 Hydrochloric acid, = 1.16g/mL to1.18g/mL, diluted1+1. 3.9 Hydrochloric acid, = 1.16g/mL to1.18g/mL, diluted1+49. 3.10 Hydrofluoric acid, 40% (m/m) 3.11 Hydrogen peroxide, 15g/L (5 volumes), approximately. Dilute hydrogen peroxide, 300g/L (100 volumes) approximately,1
17、+19. NOTESome grades of hydrogen peroxide are unsuitable for this determination. 300g/L (100 volumes) has been found satisfactory. 3.12 Iron, high purity. 3.13 Mercury. Use clean mecury. Methods of recovering used mercury include filtration through a sintered glass funnel, and distillation of the re
18、maining amalgam in an iron or mild steel pot still in a fume cupboard 1) . 3.14 Nitric acid, = 1.42g/mL. 3.15 Phenolphthalein indicator, 10g/L solution. Dissolve1g of phenolphthalein in50mL of ethanol, dilute to100mL with water and mix. 3.16 Sodium carbonate 3.17 Sodium carbonate solution, 150g/L ap
19、proximately. Dissolve150g of sodium carbonate in water, dilute to1L and mix. Prepare this solution in a polyethylene beaker and store in a stoppered polyethylene bottle. 3.18 Sodium hydrogen sulfate 3.19 Sodium hydroxide, 400g/L solution. Dissolve400g of sodium hydroxide cautiously, with stirring an
20、d cooling, in600mL of water, dilute to1L and mix. Prepare this solution in a polyethylene beaker and store in a stoppered polyethylene bottle. 3.20 Sodium hydroxide, 80g/L solution. Dissolve80g of sodium hydroxide cautiously, with stirring and cooling, in600mL of water, dilute to1L and mix. Prepare
21、this solution in a polyethylene beaker and store in a stoppered polyethylene bottle. 3.21 Sodium hydroxide, 10g/L solution. Dissolve10g of sodium hydroxide cautiously, with stirring and cooling, in600mL of water, dilute to1L and mix. Prepare this solution in a polyethylene beaker and store in a stop
22、pered polyethylene bottle. 1) Methods of Analysis Committee. Mercury cathode electrolysis and its application to steel analysis. Journal of the Iron and Steel Institute, 176, January 1954, 2936.BS6200-3.1.2:1991 2 BSI 09-1999 3.22 Sulfuric acid, = 1.84g/mL, diluted1+7. To500mL of water, add cautious
23、ly, with stirring and cooling, 125mL of sulfuric acid, = 1.84g/mL, cool, dilute to1L and mix. 3.23 Sulfuric acid = 1.84g/mL, diluted1+99. To500mL of water, add cautiously, with stirring and cooling,10mL of sulfuric acid = 1.84g/mL, cool, dilute to1L and mix. 4 Apparatus NOTEIt is essential to reserv
24、e a special set of glassware and polyethylene ware exclusively for use in these determinations. 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS700, BS846, BS1583, or BS1792, as appropriate. 4.3 Beakers, good quality seamless beakers of stainless steel, or
25、alternatively made of polytetrafluoroethylene. 4.4 Mercury cathode cell. The cell shown inFigure 1 is recommended for a test portion of1g. 4.5 Spectrophotometer, suitable for measuring absorbance at a wavelength of535nm. 4.6 Cells, having optical path lengths of0.5cm. 5 Sampling Carry out sampling i
26、n accordance with BS1837. NOTEBS6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS6200-2. 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of1g. 6.2 Blank test In paral
27、lel with the determination and following the same procedure carry out a blank test using the same quantities of all reagents, but omitting the mercury cathode electrolysis. 6.3 Determination 6.3.1 Preparation of the test solution Place the test portion in a125mL conical beaker, add15mL of sulfuric a
28、cid (3.22), cover the beaker and heat gently until solvent action ceases. For samples containing niobium, tantalum or more than1% (m/m) silicon, evaporate the solution to fuming, cool, redissolve the salts with15mL of water and allow to stand for30min. For high tungsten steel, oxidize with nitric ac
29、id(3.14), evaporate cautiously to fuming, cool, redissolve the salts with15mL of water and allow to stand for30min. For test portions not readily soluble in sulfuric acid, first dissolve in hydrochloric acid (3.7), oxidize with nitric acid (3.14), then add15mL of sulfuric acid(3.22). Evaporate to fu
30、ming, cool and redissolve the salts with15mL of water. Filter through a small paper-pulp pad and wash with hot sulfuric acid (3.23). Reserve the filtrate. 6.3.2 Recovery of insoluble aluminium Transfer the filter to a platinum vessel and ignite at as low temperature as possible until carbonaceous ma
31、tter has been removed. Moisten the residue with water, add five or six drops of sulfuric acid (3.22) and2mL of hydrofluoric acid (3.10). Evaporate to dryness, preferably under an infra-red lamp. Heat on a hot plate to complete the removal of sulfuric acid, and finally heat at700 C to800 C for5min, t
32、hen cool. Fuse the residue with0.5g of sodium hydrogen sulfate (3.18), cool, add10mL of water, and warm the vessel until the fused mass has dissolved. The fused residue of certain types of complex steel may be only partially soluble in water; in such cases, transfer the extract to a small beaker and
33、 heat to dissolve the residue as far as possible. Filter the solution through a paper-pulp pad, washing with sulfuric acid (3.23), and discard the residue. Combine the solution with the reserved filtrate from6.3.1. 6.3.3 Mercury cathode electrolysis Transfer the solution to the electrolytic cell, di
34、lute to60mL and electrolyse at2A to3A for at least90min, or until the solution is colourless. The speed of the electrolysis can be increased by using a higher current density provided that water cooling is adequate to keep the cell temperature below40 C. Free acid is liberated during electrolysis, a
35、nd this may be sufficient to retard the electrodeposition, particularly with chromium steels. The addition of10mL of sodium carbonate solution (3.17) during the later stages of electrolysis will accelerate the removal of chromium. Complete removal of iron may be confirmed by a spot test. Rinse the c
36、ell and its cover with water, and electrolyse for a further10min. Separate the electrolyte from the mercury as quickly as possible. Wash the interior of the cell and the mercury with water, adding the washings to the electrolyte. Filter through a small rapid filter paper into a250mL squat beaker and
37、 wash with water.BS6200-3.1.2:1991 BSI 09-1999 3 6.3.4 Treatment of the electrolyte Evaporate carefully to about10mL. If the solution is green at this stage, indicating incomplete removal of chromium, neutralize most of the free acid with sodium carbonate solution (3.17) and repeat the electroysis u
38、sing clean mercury. From a polyethylene measuring cylinder, add10mL of sodium hydroxide solution (3.19) to a200mL stainless steel or polytetrafluoroethylene beaker. For test portions containing more than0.060% (m/m) phosphorus add also0.2g of calcium oxide (3.5). Pour the concentrated electrolyte in
39、 slowly, rinsing in with a minimum of water. Add5mL of hydrogen peroxide (3.11) dropwise from a graduated pipette, cover the beaker, then heat to boiling and continue boiling gently for10min, avoiding undue evaporation. Remove from the source of heat, add a little paper-pulp and allow to stand for5m
40、in. Filter through a tightly packed paper-pulp pad contained in a polyethylene funnel, and collect the filtrate in a200mL polyethylene beaker. Wash with sodium hydroxide solution (3.21). NOTEAll dimensions are in millimetres. Figure 1 Cell for electrolysis with mercury cathodeBS6200-3.1.2:1991 4 BSI
41、 09-1999 Add two or three drops of phenolphthalein indicator(3.15). Neutralize by dropwise addition of hydrochloric acid (3.8) from a graduated pipette, stirring throughout with a polyethylene rod, and adding1mL in excess. If calcium oxide (3.5) has been added and the phenolphthalein indicator end p
42、oint is difficult to detect, use an external indicator paper. Cool the solution, transfer to a200mL volumetric flask, dilute to the mark and mix. 6.3.5 Spectrophotometric determination By means of a pipette, transfer a suitable aliquot to a125mL beaker, as shown inTable 1. Table 1 Aliquot data Add 5
43、mL of hydrogen peroxide solution (3.11), mix and add one drop of phenolphthalein indicator solution(3.15). Carefully neutralize by dropwise addition of sodium hydroxide solution (3.20), then add one drop excess. NOTE 1Make all the following additions by pipette, safety pipette, or burette. Add hydro
44、chloric acid solution (3.9) until the solution is colourless, then add1.0mL excess, and mix. Add5mL of acetone (3.4) and mix. Add 5.0mL of eriochromecyanine solution (3.6) and mix. Add25mL of acetate buffer solution (3.2), transfer to a100mL volumetric flask, immediately dilute to the mark and mix.
45、Allow to stand for30min at20 1 C, and then without further delay measure the absorbance of the solution at535nm wavelength in a cell with0.5cm optical path length. Determine the blank value of the reagents concurrently with the test determinations, omitting the mercury cathode electrolysis but using
46、 the same volumes of reagents and taking the same aliquot. Typical values for the absorbance of blank solutions are0.14 to0.18, depending upon the volume of the aliquot taken. NOTE 2It is important that approximately the same time interval should elapse between colour development and absorbance meas
47、urement for the test portion, the blank, and the calibration solutions. 6.4 Preparation of the calibration graph Weigh 1g portions of high purity iron (3.12) to the nearest0.001g, and transfer to six125mL conical beakers. To each add15mL of sulfuric acid (3.22), cover the beakers and heat gently unt
48、il solvent action ceases, then cool. Make additions of aluminium solution (3.1) as shown inTable 2. Table 2 Calibration data Continue by following the procedure described in6.3.3 to6.3.5, taking20mL aliquots at6.3.5. Prepare a calibration graph by plotting the absorbance of each solution against its
49、 equivalent aluminium percentage by mass. 7 Calculation and expression of results 7.1 Calculation Calculate the aluminium content Al, expressed as a percentage by mass, from the equation: where m 1is the equivalent aluminium content of the test portion in% (m/m); m 2is the equivalent aluminium content of the blank test (in% m/m); V is the volume of the aliquot taken in6.3.5 (inmL). 7.2 Precision 7.2.1 Precision data A planned trial of this method was carried out by six analysts, each from a different laboratory. Five tests were ca
