A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer.

  • Roscoe, Henry E. (Henry Enfield), 1833-1915
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer. Source: Wellcome Collection.

    511/520 (page 499)
    INDIUM. In. = 1134 307 This metal was discovered in Freiberg zinc-blende in the summer of the year 1863, by Reich and Richter, by means of spectrum analysis.1 Indium also occurs in other zinc-blendes, although present only in very small quantity. Jn order to prepare indium it is best to employ metallic zinc, such as that from Freiberg, which, however, does not contain more than 0T per cent. The metal is treated with such a quantity of hydro- chloric acid that a small portion remains undissolved, and when the solution is allowed to stand for two or three days the whole of the indium is found to be precipitated on the residual zinc. The metallic powder is then washed off from the zinc, a few drops of dilute sulphuric acid added in order to dissolve any basic zinc chloride which may be formed, and the spongy metal well washed with hot water, then treated with nitric acid, and the acid solution, without filtration, boiled down with an excess of sulphuric acid until all the nitric acid is driven off. The solution is then filtered, the residue well washed, and a large excess of ammonia added to the filtrate. The zinc, cadmium, and copper then remain in solution whilst the whole of the indium together with iion, lead, and a small quantity of zinc, cadmium, and copper remain behind. After well washing, the residue is dissolved in a small quantity of hydrochloric acid, an excess of hydrogen sodium sulphite added, and the solution boiled until it does not any longer smell of sulphur dioxide. A precipitate is thus obtained of indium sulphite, which for further purification may be dissolved in sulphurous acid; on boiling this solution the pure salt separates out,2 and this when strongly heated decomposes, leaving a residue of indium oxide. The oxide can then be reduced to metal by ignition in a current of hydrogen or by fusion with sodium. The latter method appears to be the best suited for the prepara- tion. of large quantities. For this purpose the finely-divided oxide is placed in layers in a crucible with thin slices of sodium, the mixture pressed down and then covered with a thick layer of anhydrous sodium chloride. The porcelain crucible is next placed in a Hessian crucible provided with a cover and J Journ. Trad. Chem. lxxxix. 444 ; xe. 172 ; xrii. 480. 2 Bayer, Ann. Clicm. Pharm. clviii. 372.