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.

    195/272 (page 177)
    render the whole of the silicic acid insoluble ; the dry mass is then boiled with dilute hydrochloric acid; the solution containing the bases and other acids is filtered off from the insoluble silica, which is examined according to 445. 444, The decomposition of the silicates, which are not decomposable by hydrochloric or nitric acid, is best effected by fusing them with four times their weight of a mixture of carbonate of soda and carbonate of potash. The silicate must be reduced to the finest powder, and then intimately mixed with the alkaline carbonates, also in a state of fine powder; the mixture is then to be heated, by means of a gas lamp or Berzelius spirit-lamp, in a platinum crucible, until the mixture is in a state of fusion. The crucible -is then allowed to cool; and when cold or nearly so, and still containing the fused mass, it is put into an evaporating dish containing dilute hydrochloric acid. When the fused mass is detached from the crucible, remove the crucible and evaporate the mixture to dryness, and ignite just in the same way as the solution in 443 is directed to be treated. The fixed alkalies cannot of course be sought for in that portion which has been fused with the alkaline carbonate ; to ascertain whether they are present, another portion of the silicate must be fused with hydrate of baryta. For this purpose ‘‘mix one part of the very finely pulverized sub- stance with four parts of hydrate of baryta; expose the mixture for half an hour, in a platinum crucible, to the strongest possible heat of a good Berzelius spirit-lamp or to a gas lamp, and treat the fused or agglutinated mass with hydrochloric acid and water until it is dissolved. Pre- cipitate the baryta and all the bases in the silicate, with the exception of magnesia and the alkalies, with ammonia and carbonate of ammonia; filter, evaporate to dryness, ignite, dissolve the residue in water, precipitate again with on