THE ANALYST. 369 INORGANIC ANALYSIS. Technical Estimation of Silver Bromide in Photographic Dry Plates. V. Bellach. (AZZg. Phot. Zeit., 1902, ix., 165 ; through Chein. Zeit. Rep., 1902, 276.) -The film is brought into a porcelain basin and treated in the cold with a 1 : 20 solution of potassium cyanide for about fifteen minutes. When all the silver has been dissolved the liquid is rinsed into a beaker, and warmed with strong nitric acid to drive off the hydrocyanic acid. The silver bromide is thus reproduced, and coheres into a mass which oan easily be washed by decantation. Finally, it is thrown on a tared double paper, washed thoroughly, dried at 110' or 120' C., and weighed. Alternatively, the cyanide solution may be electrolysed with a current of 3.7 to 4.1 volts at a density of 0.2 to 0.5 ampere per 100 square centimetres.F. H. L. Strong Sulphuric Acid as a Solvent in the Analysis of Tin Alloys. H. Nis- senson and F. Crotogino. (Chem. Zeit., 1902, xxvii., 984.)-This is essentially a continuation of the authors' former paper (ANALYST, xxvii., 336). In the absence of lead 0.5 gramme of the sample is heated with 7 C.C. of strong sulphuric acid for a few minutes till solution is complete. The liquid, which contains the tin, is cooled, cautiously diluted with hot water, and the yellow precipitste, comprising all the tin and antimony (the latter in the lower state of oxidation), is allowed to settle in a hot place. As it is, it filters better than the similar precipitate obtained after treatment with nitric acid, but it may be improved in this respect by oxidation, preferably by means of ammonium persulphate. After washing, it is strongly ignited with the filter- paper, and weighed as SnO, + SbO,.::: The filtrate is raised to the boiling-point and the * [Ignition of a mixture of tin and antimony oxides with the filter-paper causes loss by volstiliza- tion.-B.B.]370 THE ANALYST. copper is thrown down with thiosulphate; in the next filtrate iron, cadmium, etc., are determined. A second sample is dissolved as before, and the solution is diluted with a little water and 15 C.C. of weak hydrochloric acid. The antimony (with any copper) is precipitated with iron wire, dissolved in aqua regia, thrown down with sulphuretted hydrogen, dissolved in sodium sulphide, and the antimony itself is recovered by electrolysis.The insoluble metallic sulphides are taken up in nitric acid, and the liquid is examined for copper, bismuth, etc, If no iron and but little copper are present the antimony can be estimated by treating the original solution with hydrochloric and tartaric acids and titrating with iodine, or Gyory's direct process with potassium bromate may be employed. If a volumetric method is decided upon, the sulphuric acid must be cooled immediately the alloy is dissolved, or some of the antimony may be oxidized. In the presence of lead and tin only, the sulphuric acid solution is diluted with hot water, and a considerable quantity of ammonium oxalate is added. After cooling the lead sulphate is filtered off, and the filtrate is electrolysed with a current of 1 to 1.5 amperes per 100 square centimetres to recover the tin-such being the method for soft solders.If other metals are expected, the first solution is diluted with hot water only, the residue washed with weak sulphlfric acid, ignited and weighed as PbSO,+ SnO,+ SbO,. In the filtrate, copper, iron, cadmium, zinc, etc., are deter- mined as usual. A second sample is treated identically, but the precipitate of lead, antimony, and tin is dissolved in hot dilute hydrochloric acid, two drops of sulphuric acid are introduced, the whole is cooled, and the lead is filtered off. In the filtrate antimony is thrown down with iron wire as before, and the tin either estimated by difference or by precipitation with sulphuretted hydrogen after removal of the elemental antimony.If the solution containing iron is evaporated to free it from hydrochloric acid till fumes of sulphuric acid appear, the tin will not be thrown down quantitatively by mere dilution with water, ahd the precipitate which is obtained will be contaminated with much iron. The method is not suitable for the analysis of alloys (bronze and the like) con- taining much copper, as the dissolution does not proceed rapidly enough. F. H. L. Photometric Determination of Iron. J. I. D. Hinds and Myrtie Louise Cullum. (Joicrrt. Amer. Chem. SOC., xxiv., 848.)-This paper constitutes the first application of the photometric method to the case of coloured precipitates. For the readings a candle and simple photometric cylinder were used (Journ. Amer. Chem. SOC., xviii., 661).The iron was precipitated in a solution containing up to I per cent. of nitric acid by means of a 5 per cent. solution of potassium ferrocyanide. Since ferric ferrocyanide is soluble in exces~ of potassium ferrocyanide, the addition of the latter to the iron solution must be made drop by drop, after a precipitate has once appeared, a reeding being taken between each addition of ferrocyanide, and the lowest one being taken, since this represents the maximum opacity. If y is the percentage of iron in the solution and x the photometric reading, y may be calculated from the empirical formula 0-0302 7 y = x-8'TEE ANALYST. 371 Using this formula, results were obtained in a series of test analyses correct to 1 part of iron in 1,000,000 of solution, or, with the quantities of iron used, which were generally less than 0.01 gramme, correct to about 1 per cent. on the iron. A. G. L. The Precipitation of Ammonium Vanadate by means of Ammonium Chloride. (Zeds. onorg. Chem., xxxii., 181.)-In this reply to Gooch and Gilbert’s vindication of Gibbs’s method (supra), the author states that they appear to have misunderstood his original paper, as he himself obtained sufficiently accurate results when working with pure vanadium solutions, and that his strictures of the method only applied to the case in which tungstic as well as vanadic acid is present, as then not inconsiderable amounts of ammonium tungstate are carried down with the ammonium vanadate. The other investigators mentioned by Gooch and Gilbert also only criticised the method as a means of separating vanadic from molybdic acid. Arthur Rosenheim. A. G. L.