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.

    50/272 (page 32)
    absent. Suppose we had to examine a solution for sesqui- oxide of iron and alumina: now, if the sesquioxide of iron was present in the solution, the liquid could not have an alkaline reaction,* because sesquioxide of iron is insoluble both in the volatile and fixed alkalies; therefore, if the solution is alkaline, from one of the fixed alkalies, sesqui- oxide of iron must be absent; if the alkalinity be due to the volatile alkali, alumina, as well as sesquioxide of iron, must be absent, because alumina, as well as sesquioxide of iron, is Insoluble in ammonia. We will suppose that the solution is slightly acid, then both substances may be pre- sent; we add to the solution one of the fixed alkalies in excess, the excess will keep the alumina in solution, but the sesquioxide-of-iron precipitate will remain undissolved. The solution must be filtered, if a precipitate is formed; and to the filtrate, or to the solution which has failed to give a precipitate, must be added hydrochloric acid in excess: 1f ammonia is then added in excess, alumina, if present, will be precipitated. Suppose we had to examine a solution for ammonia and potash: as the same reagents which precipitate potash precipitate also ammonia, the latter, when present, must be got rid of before potash can be tested for ; we are therefore obliged to look for ammonia first; to ascertain if it is present, we add to a part of the solution some soluble base, as potash or soda; if present, it will be liberated from its combinations by either of these reagents, and can then be detected by the smell, &c. When present, the other portion of the solution must be evapo- rated to dryness, and the ignition continued until all the ammoniacal salt is expelled; if, after the expulsion of the ammoniacal salt, a residue remain, it must be dissolved m * Unless fixed organic matter was present, which is a condition it would be improper to consider or notice at present.