Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    85/272 (page 67)
    acid, if a free mineral acid is present. They are not pre- cipitated completely from their neutral solutions by hydro- sulphuric acid, but they are completely precipitated by that acid from their alkaline solutions in the state of sulphides. Their sulphides are insoluble in the alkalies and alkaline sulphides, with the exception of sulphide of nickel, which, under certain circumstances, dissolves to a slight extent in the alkaline sulphides, imparting thereby to the solution a brownish colour. 164. The metallic radicals of these oxides possess the following properties : manganese decomposes water at 212 F., and zinc, nickel, and cobalt decompose it at a red heat, and at common temperatures in contact with strong acids. 165. The precipitate produced by the general reagent, ‘sulphide of ammonium, after being well washed with water’ containing a little sulphide of ammonium,* must be ex- amined in the following way :—lIfit is of a light colour, NICKEL and coBatr must be absent (I 1, K1). Examine the precipitate for MANGANESE by the blowpipe test (171) ; if manganese is absent, examine the precipitate for zinc by the blowpipe test (174). When manganese is present, dissolve the precipitate in dilute hydrochloric acid; boil to expel sulphuretted hydrogen, then add carbonate of ammonia in excess and boil for some time: the manganese will be precipitated as carbonate (G3), whilst zrvo, if present, will remain in solution. Filter, and to the filtrate add sulphide of ammoniwum—when. zinc, if present, will be pre- cipitated as sulphide; confirm its presence by examining the precipitate by the blowpipe test. 166. If the precipitate is black, all the members of the group must be sought for. Examine the precipitate for * Sulphide of ammonium is added in order to prevent the precipitate from oxidizing.