摘要:

THE ANALYST. 25 INORGANIC ANALYSIS. Electrolytic Determination of Bismuth. A. Hollard and L. Bertiaux. (Bull. SOC. Chirn. 1904 xxxi. 1131-1133.)-Separation of Bismith und Copper.-The solution of the two metals in the form of sulphates (which should not contain a large excess of sulphuric acid) is brought to the boiling-point and treated with a large excess of phosphoric acid. After standing overnight the precipitate is collected and washed with dilute phosphoric acid (1 part of specific gravity 1.711 with 19 parts of water) and then with ammonium hydrosulphide and potassium cyanide solution to remove the copper. This washing solution ought to contain in 100 C.C. 5 grammes of potassium cyanide and 5 C.C. of ammonium hydrosulphide obtained by saturating a 10 per cent. solution of ammonia with hydrogen sulphide.The precipitate of bismuth phosphate is dissolved in dilute nitric acid (I l ) and the solution evaporated with 12 C.C. of sulphuric acid until abundant white fumes appear when the bismuth will have been converted into pyrophosphate. The residue is then diluted to 300 c.c. and the liquid electrolysed for twenty-four hours with a current of 0.1 ampere per square decimetre. (No other details given.) The bismuth deposited should be tested with ammonia for copper which if found should be determined colorimetricall y. Separation of Binmth and Lead-The separation of lead from bismuth in the form of sulphates is not accurate when the proportion of lead is large owing to the lead sulphate retaining a considerable amount of bismuth; whilst if a solution of bismuth in sulphuric acid containing insoluble lead sulphate be electrolysed an appreciable quantity of lead is deposited with the bismuth.This difficulty is obviated as follows The solution containing the two metals in the form of nitrates is evaporated with an excess of 12 C.C. more than the amount of sulphuric acid required to combine with the bismuth and lead present. As soon as abundant white fumes appear the liquid is cooled diluted to 300 c.c. mixed with 35 C.C. of absolute alcohol and electrolysed for forty-eight hours with a current of 0.1 ampere. Th 26 THE ANALYST. addition of the alcohol renders the lead sulphate completely insoluble without interfering with the deposition of the bismuth. The results quoted show that minute quantities of bismuth can be accurately separated from large amounts of lead by this method.C. A. M. Analysis of Commercial Tin and its Alloys. A. Hollard and L. Bertiaux. (BzdZ. SOC. Chim. 1904 xxxi. 1128-1131.)-Arsenic.-Five grammes of the tin are placed in an apparatus for distillation of the arsenic and treated with a solution of 50 grammes of ferric sulphate in 150 C.C. of hydrochloric acid and the arsenious chloride determined volurnetrically (ANALYST xxv. 301). Lead Bismuth and 1ropz.-Five grammes of the tin are dissolved in hydrochloric acid with the addition of the smallest possible quantity of nitric acid. Ammonia is then added in excess after which a current of hydrogen sulphide is introduced until the whole of the tin has dissolved. The solution is filtered from the sulphides of lead iron and bismuth and the part of the copper sulphide that has not been dissolved by the ammonium sulphide.The precipitate is washed with water and then with a solution of hydrogen sulphide and redissolved in hydrochloric acid con-taining bromine. The excess of bromine is expelled by heat and the liquid treated with hydrogen sulphide which precipitates the lead bismuth copper and the small amount of tin which was precipitated with them. This precipitate is collected and washed with a solution of hydrogen sulphide. The iron left in the solution is precipitated with ammonia after the liquid has been boiled and treated with nitric acid. The precipitate is redissolved in hydro-chloric acid reprecipitated with ammonia and the iron determined volumetrically by converting it into ferric chloride nearly neutralizing the solution with sodium bicarbonate mixing it with 5 C.C.of carbon bisulphide and an excess of a concentrated solution of potassium iodide and leaving it in the closed flask for thirty minutes, after which the liberated iodine is titrated with standard sodium thiosulphate solution-Fe2C1 + 2KI = 2FeC1 + 2KC1+ 21. The precipitate of sulphides is dissolved in hot hydrochloric acid containing bromine, solution being completed by washing with hot water. The liquid is mixed with ammonia in excess and a little potassium cyanide (to keep the copper in solution), and treated with a current of hydrogen sulphide which now precipitates only the lead and bismuth. The precipitate is collected washed with dilute ammonium hydrosulphide then with water and then with a solution of hydrogen sulphide.The sulphides are converted into sulphates by being dissolved in nitric acid contain-ing bromine and evaporation with sulphuric acid. The lead sulphate is filtered off and determined electrolytically (BuZl. SOC. Chim. xxxi. 239) whilst the bismuth is determined electrolytically in the filtrate (Conzptes Rendus 1904 366). AntZmoizy.-One gramme of the original tin is treated with aqua regia and the nitric acid subsequently expelled by repeated evaporation with hydrochloric acid. The dry residue is rendered alkaline by the addition of several drops of sodium hydroxide solution and taken up with a mixture of 200 C.C. of concentrated sodium hydrosulphide solution and 40 C.C.of a 20 per cent. solution of potassium cyanide, and electrolysed with a current of 0.1 ampere only the antimony being deposited (ANALYST xxviii. 228) THE ANALYST. 27 Copper. % 0.480 0.000 0.040 0.030 -- _ Copper and Sulphur.-Five grammes of the tin are treated with nitric acid and the mixture evaporated to dryness on the water-bath. The residue is taken up with water acidified with nitric acid the liquid decanted and the residue washed with the same acidified water. The copper in the filtrate and washings is separated and determined by electrolysis. The sulphur in the solution is determined by evaporating the liquid on the water-bath taking up the dry residue with water filtering the solution adding a few drops of hydrochloric acid and precipitating the sulphate with barium chloride.Compositioyz of Commercial Samples.-The following results were thus obtained : Arsenic. --% 0.079 0.022 0-034 0-118 0.033 Commercial Tin. Zinc. % -- German . . .,. Swiss . . . Commercial sample . . . Chinese . . . Malaccan . . . - -~ - _ _ Lead. -% 0.498 -Anti-mony. % 0-545 1.174 0.110 0-044 -Nickel I and 1 Iron. Cobalt. i % I % l -I --0.0281 0.040 - I 0.037 0-014 I 0.009 -Bis-muth. % 0.060 0.580 --I Alloys of Tin a d Lead (Solders etc.).-One gramme of the finely-divided alloy is mixed with 10 grammes of copper and treated with 52 C.C. of nitric acid in a 350 C.C. beaker. The nitric acid used is diluted with a little water the amount of which is smaller in proportion to the quantity of tin present.The liquid in the beaker is diluted to 300 c.c. and heated on the water-bath for a short time to make the oxide of tin collect at the bottom after which it is cooled and the lead separated electro-lytically in the form of peroxide (Bull. Xoc. Clzim. 1904 293). The spiral immersed in the liquid ought to reach nearly to the bottom of the flask. Under these con-ditions the oxide of tin does not interfere with the separation of the lead. C. A. M. An Improvement on Drown and Shimer’s Methods of determining Silicon in Iron. J. Thill. (Zeit. anaZ. Chem. 1904 xliii. 552 553.)-An objection to these methods is the long time required for the evaporation of acids used whilst if a naked flame be used instead of the water-bath for heating there is danger of loss.The following modification is stated to give accurate results within an hour. From 1 to 2 grammes of the powdered crude iron (according to the amount of silicon) are placed in a beaker holding 400 to 500 c.c. and treated with 50 to 70 C.C. of a solution prepared as follows A litre of concentrated sulphuric acid is diluted with an equal volume of water and mixed with a litre of nitric acid (specific gravity 1.40) and a solution of 240 grammes of ammonium chloride in a litre of water. After adding the required amount of this reagent to the iron the liquid is heated to dissolve the iron and evaporated on wire gauze over a Bunsen flame until white fumes appear. The residue is then diluted with about 100 C.C.of water and heated until the sulphates have con~pletely dissolved after which the liquid is filtered and the insoluble residue washed with hot water then with 10. C.C. of hot dilute hydro-chloric acid and again with hot water. Finally the filter and its contents are ignited while still moist then heated in a muffle and weighed. C. A. M 28 THE ANALYST. The Colorimetric Determination of Carbon in Steel. H. C. Boynton and H. K. (Xtahl und Eiserz 1904 1070 ; through Cltem. Zeit. Rep 1904 xxiii. 283.)-The condition of the carbon in steel determines the amount of colour produced in Eggertz process. Three samples were taken of a piece of steel containing 0.48 per cent. of carbon, and heated to 1200O C. The first was cooled rapidly in an air blast the second was allowed to cool spontaneously in the air while the third was left in the furnace and cooled very gradually.The analysis of the blast-cooled sample showed only 0.34-0-35 per cent. of carbon that of the air-cooled sample 0.36-0-39 per cent. while the sample cooled in the furnace gave the full (0.48 per cent.) amount. H. A. T. APPARATUS. Note on the Durability of Platinum Crucibles. G. Siebert. (Chewz. Zeit., 1904 lxxiv. 869.)-The author who is a member of Messrs. G. Siebert’s Platinum Works Hanau considers that the occasional rapid deterioration and fracture of platinum crucibles etc. is not always due to the presence of chemical impurities, such as iridium but rather to the physical properties of the platinum. H e finds that when proper precautions are taken to obtain the highest possible degree of homogeneity in the platinum in all stages of manufacture the crucibles are practically indestructible.Where however such precautions are not taken though they may be made with pure metal deterioration is very rapid in the articles. H. A. T. OBITUARY NOTICE. THOMAS A. POOLEY B.Sc. F.I.C. WE regret to record the death after a prolonged illness of Mr. Thomas A. Pooleg, B.Sc. F.I.C. for many years Public Analyst for the County of Essex and the Borough of West Hem and an old member of the Society. Mr. Pooley who was sixty-three years of age at the time of his death was educated first in France and subsequently at University College and King’s College London. He took an honours science degree st London University in 1864 with special distinction in chemistry. For a number of years he directed his attention chiefly to the chemistry of brewing, being for a time Editor of the Brewers’ Guardian and for a number of years a regular contributor to the Bmzoers’ Journal. During the later part of his life he devoted himself chiefly to food analysis in connection with the duties of his public appoint-ments already referred to. He rarely attended the meetings of the Society and was therefore personally unknown to very many of his colleagues but by the few who knew him his kind a d genial friendship was much prized PLATES TO ILLUSTRAT

ISSN:0003-2654    

DOI:10.1039/AN93055BA001

出版商:RSC    

年代:1930

数据来源: RSC