British Chemical Standard – bottles of 100g of finely divided material graded 150µm (100 mesh) for chemical analysis. Page 2 of 2 BCS-CRM No. 242/2 (ECRM 555-1) FERRO-TUNGSTEN NOTES ON METHODS USED CARBON All Analysts determined carbon by combustion in oxygen using either red lead or a mixture of pure iron and pure tin as flux. Nos. 1 and 4 completed by non-aqueous titration (Jones et al., Analyst, 1965, 90, 623; 1966, 91, 399). No. 2 used the conventional low pressure method (Cook and Speight, Analyst, 1956, 81, 144) whereas No. 5 used a modification of this method (Dunnill and Kent, Metallurgia, 1970, 81, 125). Nos. 3 and 7 completed by infrared absorption. Analyst No. 2 also used an infrared absorption method and found 0.026%. SILICON Analysts Nos. 1, 5 and 6 determined silicon by titration after precipitation as potassium silicofluoride; Nos. 1 and 6 followed the procedure of the ASTM Method Designation E31-63. Nos. 2, 4 and 7 determined silicon gravimetrically. No. 2 fumed with a mixture of sulphuric, phosphoric and perchloric acids and took up the residue in tartaric acid solution. No. 4 fumed with sulphuric acid and took up the residue in oxalic acid solution; the solution was made ammoniacal and then acidified again before filtering off the silica. No. 7 fumed with a mixture of phosphoric acid and perchloric acid. No. 3 determined silicon by atomic-absorption spectroscopy. Analysts Nos. 3 and 5 also determined silicon gravimetrically and found 1.63% and 1.77% respectively. ALUMINIUM Analysts Nos. 1 and 6 determined aluminium by titration via the oxinate; both Analysts first separated tungsten as tungstic oxide and then carried out a sodium hydroxide separation to remove iron. Nos. 2 and 5 determined aluminium photometrically with eriochrome-cyanine after removal of tungsten. No. 3 mixed the sample with graphite containing cobalt as internal standard and analysed by AC arc spectroscopy. No. 4 determined aluminium by atomic-absorption spectroscopy. Analyst No. 2 also determined aluminium by titration via the oxinate and found 0.15%. TIN All Analysts except No. 3 determined tin by titration. Nos. 1, 2, 4, 5 and 7 carried out a preliminary separation of the tin as sulphide according to the British Standard Tin Method 2*. No. 3 mixed the sample with graphite containing cobalt as internal standard and analysed by AC arc spectroscopy. TUNGSTEN All Analysts decomposed the sample with hydrofluoric/nitric acid mixture and determined tungsten gravimetrically as the oxide. In most cases cinchonine was added to aid precipitation and in all cases a correction was applied for any iron in the final precipitate by fusing with sodium carbonate, leaching with water and weighing the insoluble residue. After filtering off the tungstic oxide precipitate, No. 2 determined the small amount of soluble tungsten in the filtrate by the photometric toluene-3:4-dithiol method. SULPHUR Both Analysts detemined sulphur by combustion. *Methods for Sampling and Analysis of Iron, Steel and Other Ferrous Metals, B.S. Handbook No. 19, first published in 1970 by the BSI, 389 Chiswick High Road, London. W4 4AL.

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