Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![between 100° and 150°, but otherwise more or less brittle; it fuses retLTon cVrcoal before the blowpipe, boils afterwards, and bm-ns rejiauy on_ ^^^^^ . . oflp^vi^ite fumes, and coating the char-. Totl supp't w^^^^^ - hydrochloric and sS^^hS aclr with evolution of hydrogen ; in dilute mtric acid, wi h evoCorof nitTous oxide; in more concentrated nitric acid, with ^^oxfdTof'inc and its hydrate are white powder., which are Insoluble in water, but dissolve readUy - hydroch oric, rixtric and sulphuric acids. Oxide of zinc acquires a lemon-yellow tint when heaCrbut resumes its original white colour as it coo s; when ignited before the blowpipe, it becomes briUiantly incandescent. 3 The salts of oxide of zinc are colourless; some of them ai^ soluble in water, the others in acids. The neutral sa ts of zmc which are soluble in water redden litmus-paper, and are readily ^^P^^^^^^J heat, with the exception of sulphate of zinc, which is not decomposed at a duU red heat, but readHy undergoes decomposition at a higner temperature. Chloride of zinc is volatile at a red heat. 4 Sulphuretted hydrogen throws down a part of the zmc trom neutral solutions of zinc salts containing strong acids m the form ot white hydrated sulphide of zinc,ZnS [ZnS]. On the other hand, from neutral solutions of zinc salts containing weak acids, acetate ot zmc for example, or from solutions of neutral zinc salts which contam neutral salts of weak acids in sufficient quantity (for example acetate ot soda or sulphocyanate of ammonium), sulphuretted hydrogen throws down ail the zinc. In acid solutions, no precipitate is produced if the free acid is one of the strong acids, and is present in sufficient quantity. Acid sulphates of the alkahes prevent the precipitation only when present m abundance ; with smaH quantities, part of the zinc is precipitated.^ AU the zmc is thrown down from a solution of zinc oxide in acetic acid. 5. Sulphide of ammonium throws down from neutral, and sul- phuretted hydrogen from alkaline solutions the whole of the metal as hydrated sulphideofzinc,inthe form of a white precipitate. Chloride of ammonium greatly promotes the separation of this precipitate. From very dilute solutions, the precipitate separates only after long standmg. It is not redissolved by an excess of sulphide of ammonium, or by potassa or ammonia; but dissolves readUy in hydrochloric acid, mtric acid, and dilute sulphuric acid. It is insoluble in acetic acid. 6. Potassa and soda thiw down hydrated oxide of zmc,. ZnO,HO [ZnHjO^l, in the form of a white gelatinous precipitate, which is readily and completely redissolved by an excess of the precipitant. On boihng these alkahne solutions, they remain unaltered if concen- trated ; but if dilute, nearly the whole of the oxide of zinc separates as a white precipitate. Chloride of ammonium added to alkaline solutions, not containing a large excess of potassa or soda, produces a white precipitate of hydrated oxide of zinc, which, however, redissolves on addition of more chloride of ammonium; solutions which contain a large excess of potassa or soda give no precipitate with chloride of am- monium (difference between oxide of zinc and alumuia). 7. Ammonia also produces a precipitate of hydrated oxide of zinc in solutions of zinc salts, if they do not contain a large excess of free acid ; this precipitate dLssolves readily in an excess of the precipi- tant ; the concentrated solution becomes turbid when mixed with water,](https://iiif.wellcomecollection.org/image/b21966953_0143.jp2/full/800%2C/0/default.jpg)
