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.

    49/272 (page 31)
    with them an insoluble salt; but, in the generality of cases, they cannot be precipitated from their alkaline solutions by a salt, the acid of which forms with them a salt insolu- ble in a neutral or acid solution, or by a soluble base in which they are insoluble; before they can be precipi- tated from alkaline solutions either by salts or bases, we must, in the generality of cases, neutralize the alkali, in which they are dissolved, by some acid. (Experiment, paragraph 70.) 74. The volatile base, ammonia, if in the free state, is at onee distinguished by the smell; but when it is present in solution, in the form of a salt, the salt must be decomposed by the addition of some stronger base, before the ammonia can be detected. 75. We will now give a few examples* as illustrations. Suppose we had to examine a liquid for baryta and lime: they might be present in the solution either in the uncom- bined state or as salts; and as chromate of baryta is insolu- ble, and chromate of lime soluble, we might add to the solution a soluble chromate—say, chromate of potash. If we obtained a precipitate by the soluble chromate, baryta must be present ; if we obtained no precipitate, it must be absent: to the filtrate from the chromate of baryta pre- cipitate, or to the solution which has failed to give a pre- cipitate with the soluble chromate, we must add some acid, or a salt containing an acid, which forms with hme an insoluble salt—say we add oxalic acid or oxalate of am- monia; if either of these reagents produces a precipitate, lime is present ; if 14 does not produce a precipitate, lime is * The teacher eught te give the student three or four solutions on each example; some of the solutions containing one of the substances named in the example, some containing both of the substances named in the example.