Instruction in chemical analysis : (Qualitative) / With a preface by Prof. Liebig. Edited by J.L. Bullock.
- Carl Remigius Fresenius
- Date:
- 1846
Licence: Public Domain Mark
Credit: Instruction in chemical analysis : (Qualitative) / With a preface by Prof. Liebig. Edited by J.L. Bullock. Source: Wellcome Collection.
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![of zinc, the whole of the metal as sulphuret of zinc, in the form of a white precipitate. This precipitate is not redissolved hy an excess of hydrosulpliuret of ammonia, nor by potass or ammonia : blit it dissolves readily in hydrochloric acid, nitric acid, and dilute sulphuric acid. 5. Potass and ammonia throw down from solutions of salts of zinc, hydrated oxide of zinc (Zn 0, H O) in the form of a white gelatinous precipitate, which is readily and completely redissolved by an excess of the precipitant. 6 Carbonate of potass produces in solutions of salts of zinc a precipitate of basic carbonate of zinc (3 [Zn O, HO]+ 2 [Zn O, CO,]) which is insoluble in an excess of the precipitant. The presence of salts of ammonia prevents the formation of this precipitate, and the addition of such salts causes the re-solution of precipi- tates already formed, owing to the ammoniacal salts combining with the oxide of zinc to soluble double salts of oxide of zinc and ammonia. 7. Carbonate of ammonia also produces in solutions of salts of zinc a precipitate of basic carbonate of zinc, but this pre- cipitate redissolves upon further addition of the precipitant. 8. When a mixture of oxide of zinc, or of one its salts with carbonate of soda is exposed to the reducing flame of the blow- pipe, the charcoal support becomes covered with a slight incrus- tation of oxide of zinc, which presents a yellow color while hot, and turns white upon cooling. This incrustation is caused by the reduced metallic zinc volatilizing at the moment of its reduc- tion, and reoxidizing in passing through the outer flame. 9. If oxide of zinc, or one of the salts of zinc, be moistened with solution of protonitrate of cobalt, and subsequently heated before the blow-pipe, an unfused mass will be obtained, of a beautiful green color; this mass is a compound of oxide of zinc with protoxide of cobalt.](https://iiif.wellcomecollection.org/image/b29300940_0124.jp2/full/800%2C/0/default.jpg)
