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.

    237/272 (page 219)
    lime and lead, alumina, peroxide of iron and their phosphates, the chlorides of silver and lead, fluoride of calcium, silicates, silica, and sulphur. ; 592. A small portion of the residue, insoluble in water and acids, is heated ona slip of platinum foil. If sulphurous acid is evolved along with the volatilization of the whole of the substance, sulphur only can be present. When other substances are present, add to another small portion a drop of sulphide of ammonium. If the colour remains white, silver, lead, and probably iron, are absent. 593. A small quantity of the dry residue, in the state of a very fine powder, is mixed with four times its weight of carbonate of soda and potash. The mixed mass is placed in a platinum crucible,* and heated over a Berzelius spirit lamp for about half an hour; or, what is still better, the platinum vessel is placed within a Hessian crucible con- taining a little carbonate of magnesia, and exposed to a full red heat, for the same length of time, ina furnace. The magnesia is employed to prevent the platinum from coming in contact with the Hessian crucible. 594. On cooling, the fused mass is boiled with water, and filtered. The filtrate is to be examined for the acids and alumina, the residue for the bases. 595. Examination of the jiltrate—To one portion of the filtrate add hydrochloric acid until the solution is distinctly acid; evaporate to dryness, and ignite until acid. fumes are no longer evolved. To the dried mass add dilute hydro- chloric acid, and boil; if a residue remains, silicic acid is present. To the filtrate from the silica add ammonia in * The compounds of the easily reduced metals, such as silver, lead, &e., must not be fused in platinum vessels, as they form alloys with that metal, which greatly injures or altogether destroys the platinnm vessel: porcelain crucibles must therefore be employed in such cases.