BS-6200-3.1.6-1991.pdf

BRITISH STANDARD BS 6200-3.1.6: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.1 Determination of aluminium Subsection 3.1.6 Permanent magnet alloys: volumetric method Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 20 December 1991 © BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment 91/38341 DC ISBN 0 580 20225 9 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 and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 © BSI 09-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3Reagents1 4Apparatus2 5Sampling3 6Procedure3 7Calculation and expression of results4 8Test report4 Figure 1 Cell for electrolysis with mercury cathode2 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 ii © BSI 09-1999 Foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method 2 for the determination of aluminium in BSI Handbook No. 19, to which it is technically equivalent. BS 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 Part 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. 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, pages 1 to 4, an inside back cover 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. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 © BSI 09-19991 1 Scope This Subsection of BS 6200 describes a volumetric method for the determination of acid soluble aluminium in permanent magnet alloys. The method is applicable to alloys containing 5 % to 15 % aluminium, 7 % to 35 % nickel, 10 % to 30 % cobalt, 0.5 % to 8 % copper, up to 3 % titanium, up to 6 % niobium, all percentage by mass, and the remainder iron. NOTEThe titles of the publications referred to in this Subsection of BS 6200 are listed on the inside back cover. 2 Principle Major amounts of interfering elements are removed by mercury cathode electrolysis followed by precipitation with cupferron. Any remaining traces of interfering elements are complexed in ammoniacal tartrate-cyanide solution from which the aluminium is precipitated with quinolin-8-ol. The determination is completed by titration of the quinolin-8-ol with potassium bromate and sodium thiosulfate. 3 Reagents During the analysis use only reagents of recognized analytical grade and only grade 3 water as specified in BS 3978. WARNING. Prepare solutions 3.3 and 3.4 in a fume cupboard. 3.1 Ammonia solution, density Ô = 0.91 g/mL. 3.2 Ammonia solution, Ô = 0.91 g/mL, diluted 1 + 1. 3.3 Ammonium sulfide solution, Ô = 1.01 g/mL. Pass a rapid stream of hydrogen sulfide gas from a generator or cylinder through 1 L of ammonia solution (3.2) until the density is 1.01 g/mL approximately. 3.4 Ammonium sulfide wash solution. Add 5 mL of ammonia solution (3.1) to 950 mL of water and pass hydrogen sulfide gas from a generator or cylinder until just acid to litmus paper. Add a further 5 mL of ammonia solution (3.1), dilute to 1 L and mix. 3.5 Cupferron, 50 g/L solution. Dissolve 5 g of cupferron (also known as N-nitroso-N-phenylhydroxylamine, ammonium salt) in water, dilute to 100 mL and mix. The solid reagent and its solution deteriorate in storage. Prepare this solution from fresh reagent immediately before use. 3.6 Cupferron-acid wash solution. To 900 mL of water add 10 mL of sulfuric acid (3.21) and 5 mL of cupferron solution (3.5), dilute to 1 L and mix. Prepare this solution from fresh reagent immediately before use. 3.7 Hydrochloric acid, Ô = 1.16 g/mL to 1.18 g/mL. 3.8 Hydrochloric acid, Ô = 1.16 g/mL to 1.18 g/mL, diluted 1 + 1. 3.9 Hydrochloric acid, Ô = 1.16 g/mL to 1.18 g/mL, diluted 1 + 49. 3.10 Indigo carmine solution, 10 g/L solution. Dissolve 1 g of indigo carmine in 50 mL of water, filter, dilute to 100 mL and mix. 3.11 Mercury. Use clean mercury. Methods of recovering used mercury include filtration through a sintered glass funnel, and distillation of the remaining amalgam in an iron or mild steel pot still in a fume cupboard1). 3.12 Methyl red, 1 g/L solution. Dissolve 0.1 g of methyl red in 60 mL of ethanol, dilute to 100 mL with water and mix. 3.13 Nitric acid, Ô = 1.42 g/mL. 3.14 Potassium bromate, standard solution. Dissolve 4.954 g of potassium bromate, (previously dried to constant weight at 105 °C), and 50 g of potassium bromide (3.15) in water. Cool, transfer to a 1 L volumetric flask, dilute to the mark and mix. 1 mL of the solution is equivalent to 0.4 mg of aluminium. 3.15 Potassium bromide 3.16 Potassium cyanide, 100 g/L solution. Dissolve 10 g of potassium cyanide in water, dilute to 100 mL and mix. 3.17 Potassium iodide, 200 g/L solution. Dissolve 20 g of potassium iodide in water, dilute to 100 mL and mix. 3.18 Quinolin-8-ol, 50 g/L solution. Dissolve 5 g of quinolin-8-ol (also known as 8-hydroxyquinoline and oxine) in 6 mL of acetic acid, Ô = 1.048 g/mL to 1.050 g/mL, dilute to 100 mL and mix. 3.19 Sodium thiosulfate, standard solution. Dissolve 44 g of sodium thiosulfate, Na2S2O3.5H2O, in water containing 0.1 g of anhydrous sodium carbonate. Transfer to a 1 L volumetric flask, dilute to the mark and mix. 1 mL of the solution is equivalent to approximately 0.4 mg of aluminium. 1) Methods of Analysis Committee. Mercury cathode electrolysis and its application to steel analysis. Journal of the Iron and Steel Institute, January 1954, 29-36. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 2 © BSI 09-1999 3.20 Starch indicator, 5 g/L solution. Make a suspension of 0.5 g of starch in 10 mL of water. Pour into 80 mL of boiling water. Cool, dilute to 100 mL and mix. 3.21 Sulfuric acid, Ô = 1.84 g/mL. 3.22 Sulfuric acid, diluted 1 + 1. To 40 mL of water, add cautiously 50 mL of sulfuric acid (3.21). Mix, cool, dilute to 100 mL and mix. 3.23 Sulfuric acid, diluted 1 + 9. To 400 mL of water, add cautiously 100 mL of sulfuric acid (3.21). Mix, cool, dilute to 1 L and mix. 3.24 Tartaric acid, 200 g/L solution. Dissolve 20 g of tartaric acid in water, dilute to 100 mL and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with class A of BS 846, BS 1583, or BS 1792, as appropriate. 4.3 Mercury cathode cell. The cell shown in Figure 1 is recommended for a test portion of 1 g. Figure 1 Cell for electrolysis with mercury cathode Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 © BSI 09-19993 5 Sampling Carry out sampling in accordance with BS 1837. NOTEBS 6200-2, which will supersede BS 1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS 6200-2. 6 Procedure 6.1 Test portion For aluminium contents up to 10 % (m/m) weigh, to the nearest 0.001 g, a test portion of 1 g. For higher aluminium contents weigh a 0.5 g test portion. 6.2 Blank test In parallel with the determination and following the same procedure carry out a blank test using the same quantities of all the reagents. 6.3 Determination 6.3.1 Preparation of the test solution Place the test portion in a 400 mL conical beaker add 30 mL of sulfuric acid (3.23), cover the beaker and heat gently until all solvent action ceases. Oxidize with 2 mL of nitric acid (3.13). Boil, dilute to 100 mL and filter through a paper-pulp pad. Wash the beaker and pad eight times with hydrochloric acid (3.9) and twice with hot water. Cool the filtrate and transfer to a 500 mL volumetric flask, dilute to the mark and mix. Using a 100 mL volumetric flask, take a 100 mL aliquot, transfer to a 250 mL conical beaker, and evaporate to fuming. Continue the fuming for 5 min, cool and dilute to 50 mL. Boil to dissolve salts and cool. 6.3.2 Mercury cathode electrolysis Transfer the solution to the electrolytic cell, rinsing the beaker with the minimum of water. Electrolyse the solution for 1 h at 1.5 A to 2.5 A. Transfer the solution to a 250 mL beaker, wash the cell with water, and adjust the volume to approximately 100 mL. Add 20 mL of sulfuric acid (3.22) and cool the solution to room temperature. 6.3.3 Removal of interfering elements Add cupferron solution (3.5) slowly, with stirring, until precipitation is complete as indicated by the coagulation of the precipitate; further addition of cupferron will produce only a white transient precipitate of the free base. Add 1 mL of excess cupferron solution, stir in a little paper-pulp, filter through a paper-pulp pad, and collect the filtrate in a 400 mL beaker. Wash the precipitate with cold cupferron-acid wash solution (3.6) and discard the precipitate. To the filtrate add 20 mL of nitric acid (3.13) and evaporate to fuming. If necessary make further additions of the nitric acid and repeat the evaporation to fuming, until organic matter is destroyed. Cool, add 30 mL of water and heat until the salts are dissolved. Dilute to 70 mL, add 5 mL of tartaric acid solution (3.24) and neutralize with ammonia solution (3.2) using methyl red indicator (3.12). Add 10 mL of potassium cyanide solution (3.16), heat to 60 °C and add 25 mL of ammonium sulfide solution (3.3). Digest at 60 °C for 10 min and cool. Filter through a paper-pulp pad into a 400 mL beaker and wash with ammonium sulfide wash solution (3.4), ensuring that the final volume does not exceed 200 mL. 6.3.4 Separation of aluminium Heat to boiling and add quinolin-8-ol solution (3.18) dropwise from a burette, stirring throughout the addition. (An addition of 8 mL of quinolin-8-ol solution will precipitate 10 mg of aluminium, equivalent to 5 % (m/m) aluminium in a 1 g test portion.) Digest at 90 °C for 10 min, filter through a paper-pulp pad and wash with hot water. Dissolve the precipitate from the pad into a 500 mL stoppered flask with 100 mL of nearly boiling hydrochloric acid (3.8) and wash the pad several times with hot water. Dilute the solution to approximately 200 mL and cool. 6.3.5 Titration of quinolin-8-ol Add three drops of indigo carmine solution (3.10) and titrate with potassium bromate solution (3.14) until the blue tint of the indicator is discharged. Add three more drops of indigo carmine indicator (3.10) and continue the titration until the solution assumes a clear yellow colour, then add a further 2 mL of potassium bromate solution (3.14). Stopper the flask and allow to stand for 5 min. Remove the stopper, add 10 mL of potassium iodide solution (3.17), mix, and titrate with sodium thiosulfate solution (3.19) until the brown iodine colour is almost discharged. Add 5 mL of starch indicator solution (3.20) and continue the titration until the blue starch-iodide colour is discharged. Record the volumes of both titrants used for the test portion, and for the blank test. 6.3.6 Standardization of the sodium thiosulfate solution Transfer 100 mL of hydrochloric acid (3.8) to a 500 mL stoppered flask, dilute to 200 mL, and add 25 mL of potassium bromate solution (3.14) from a burette. Stopper the flask and allow to stand for 5 min. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 4 © BSI 09-1999 Remove the stopper, add 10 mL of potassium iodide solution (3.17), mix, and titrate with sodium thiosulfate solution (3.19) until the brown iodine colour is almost discharged. Add 5 mL of starch indicator solution (3.20) and continue the titration until the blue starch-iodide colour is discharged. Record the volume Vf, of sodium thiosulfate used. 7 Calculation and expression of results 7.1 Calculation Calculate the factor F of the sodium thiosulfate solution (3.19) from the equation: F = 25/Vf where Vf is the volume of sodium thiosulfate used in 6.3.6. NOTEPotassium bromate (3.14) is equivalent to 0.4 mg of aluminium per millilitre. Calculate the aluminium content Al expressed as a percentage by mass from the equation: where V1 is the volume of potassium bromate solution (3.14) used in the test portion titration (in mL); B1 is the volume of potassium bromate solution (3.14) used in the blank titration (in mL); V2 is the volume of sodium thiosulfate solution (3.19) used in the test portion titration (in mL); B2 is the volume of sodium thiosulfate solution (3.19) used in the blank titration (in mL); m is the mass of the test portion (see 6.1) (in g). 7.2 Precision This procedure has a precision of approximately ± 0.15 % (m/m). 8 Test report The test report shall include the following information: a) all information necessary for the identification of the sample, the laboratory and the date of analysis; b) the method used, by reference to this Subsection of BS 6200; c) the results, and the form in which they are expressed; d) any unusual features noted during the determination; e) any operation not specified in this British Standard or any optional operation which may have influenced the results. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.1.6:1991 © BSI 09-1999 Publication(s) referred to BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 1792, Specification for one-mark volumetric flasks. BS 1837, Methods for the sampling of iron, steel, permanent magnet alloys and ferro-alloys. BS 3978, Specification for water for laboratory use. BS 6200, Sampling and analysis of iron, steel and other ferrous metals. BS