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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![§§ 33, 39.] ^5 y. Heavy Metals and their Oxides. § 38. 1. Zinc, Zn [Zn]. Zinc of good quality is selected, which should leave but little'residue when dissolved in dilute sulphuric acid, and, above all, must be per- fectly free from arsenic. The method described in § 132, 10, wiU serve to detect the presence of the slightest trace of the latter. The metal is fused and poured from a height of 4 or 5 feet, in a thm stream, into a \ar^e vessel of water. Zinc which contains arsenic must be rejected, as ihere is no simple process of purification known which will remove every trace of arsenic (Eliot and Storer).* Uses.—ln qualitative analysis zinc is used for preparing hydrogen, a'^o arseniuretted and antimoniuretted hydrogen gases (compare § 131, 10, and § 132, 10); it is also employed to precipitate some metals from their solutions; the zinc simply displacing the other metal, CuO,S03 + Zn = ZnO,S03 + Cu [CuSO,+Zn = ZnSO, + Cu]. Zinc is sometimes used in the detection of sulphurous acid and phos- phorous acid; before being used for this purpose, it must be tested for sulphide of zinc or phosphide of zinc, as the case may be, see §§139 and 148. 2. Iron, Fe [Fe]. Iron reduces many metals and precipitates them from their solutions in tie metalhc state. It is used especially for the detection of copper, which is precipitated upon it with its characteristic colour. ^ Any clean surface of iron, such as a knife-blade, a needle, a piece of wire, &c., will .serve for this purpose. 3. Copper, Cu [Cu]. Copper is used to effect the reduction of mercury, and sometimes of arsenic ; any clean surface of copper, such as copper foil or copper wire, may be employed for this purpose. § 39. 4. Hydrate of Oxide of Bismuth, Bi03,H0 [BiHOj. Preparation.—Bismuth, freed from arsenic by fusion with hepar mlphuris, is dissolved in dilute nitric acid^ the solution diluted until a slight permanent precipitate is produced, and then filtered and evaporated until it crystallizes. The crystals are washed with water containing nitric acid, and triturated with water, ammonia in excess is then added, and the mixture allowed to digest for some time; the white precipitate thus produced is collected, washed, and dried. Tests.—The hydrate of bismuth (commercial basic nitrate of bismuth * According to Gunning (Scheikundige Bijdragon, Deel I. Ni\ ], p. 113), the jnmfication riiay be effected by repeated fusion with a mixture of carbonate of soda and sulphur, whilst 8elmi (Zeit. aual. Ciiem., 22, 7G) states that the arsenic may be removed by treating the melted zinc with chloride of ammonium.](https://iiif.wellcomecollection.org/image/b21966953_0079.jp2/full/800%2C/0/default.jpg)
