Elements of chemistry, in two volumes / by John Murray.

  • Murray, John.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry, in two volumes / by John Murray. Source: Wellcome Collection.

    78/768 (page 66)
    regarded as altogether distinctive. They are usually said to be insipid; but there are three of them, barytes, stron- tites, and lime, which have a strong taste : they have also been considered as insoluble in water; but these earths are soluble to a certain extent. Infusibility is a character less equivocal, as there is none of them but what requires a very intense heat for its fusion. They are altogether un- inflammable, a property obviously arising from their being substances saturated with oxygen. Barytes, however, ab- sorbs oxygen at a high temperature, a property in which it resembles the fixed alkalis. In common with metallic oxides, they are destitute of metallic lustre and opacity. The earths like the alkalis combine with the acids, forming salts, which, in the due proportions, are neutral. There is an exception to this in one earth, silex, which, in the humid way, scarcely unites with any acid but the fluo- ric, and with it does not produce the state of neutraliza- tion. It is the substance, therefore, which is at once most remote from the alkalis, and from the metallic oxides ; and, indeed, by some chemists, it has been regarded as more analogous to an acid. One property has been assigned as distinctive of the earthy from the metallic salts, that the solutions of the former are not precipitated by the triple prussiate of po- tash, or ferrocyanate of potash as it is frequently called. This is not, however, without exceptions; the earth nam- ed Yttria, and also, as Klaproth has affirmed, zircon, gi- ving precipitates with this test. In general, the earthy salts are not much altered by infusion of galls, a re-agent which so sensibly affects metallic salts : they are generally of a white colour. Yttria affords also, however, an ex- ception to these, some of its salts having a red colour, and being precipitated by infusion of galls : this colour, how- ever, is said to depend on impurity.