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.

    46/272 (page 28)
    practice to add the reagents with such mathematical accu- racy ; we are therefore obliged to add, in order to ensure the complete decomposition of a salt of this kind, the soluble base in excess; and i this excess, or in this wncom- bined portion, some of the insoluble bases dissolve, being soluble in the free soluble bases. One of the insoluble bases (oxide of zinc) is soluble both in the volatile and fixed alkalies; some of the others are soluble in ammonia, but insoluble in the other two; some are soluble in potash and soda, but insoluble in ammonia; others are insoluble in each of the three alkalies. And there are some, although insoluble in ammonia, which are not precipitated by it, if salts of ammonia are present, and are only partly preci- pitated by the fixed alkalies under these circumstances. 67. The properties which the insoluble bases display, with regard to ammonia and the fixed alkalies, are exhi- bited in the table (page 29), which the student must study with the aid of the experiments. 68. To a solution of sesquichloride of iron add a solution of caustic soda in excess; hydrate of the sesquioxide of iron will precipitate, and will not be redissolved by an ex- cess of the caustic soda. 69. To a solution of sesquichloride of chromium add a cold solution of caustic soda, until the precipitate which first appears is redissolved; then boil the solution until the hydrate of the sesquioxide of chromium once more pre- cipitates. 70. Add to a solution of sulphate of alumina caustic soda, until the precipitate which first forms is redissolved ; then add hydrochloric acid until the solution manifests an acid reaction; and, finally, ammonia in excess, which will cause the precipitation of hydrate of alumina. 71. We will now attempt to show how the precipitation