Volume 2

A system of chemistry of inorganic bodies / By Thomas Thomson.

  • Thomson, Thomas, 1773-1852.
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: A system of chemistry of inorganic bodies / By Thomas Thomson. Source: Wellcome Collection.

    61/968 (page 43)
    SELENIOUS ACID. 2 atoms sulphur = 4 5 atoms oxygen = 5 9 and the equivalent number for it must be 9.* The salts which this acid forms (and which are very curious) have been examined in detail by Dr. Heeren of Hamburg.+ An account of them will be given in a subsequent part of this work. SECTION VIII.—ACIDS OF SELENIUM AND TELLURIUM. Selenium, so far as we know at present, forms only two acids with oxygen, analogous, so far as their composition goes, to the sulphurous and sulphuric acids. ‘These acids are the selenious and selenic acids. 1. Selenic Acid. I have given the history, preparation, and properties of this acid so far as they are known in the first volume of this work (p. 290). It is a compound of | 1 atom selenium : 5 3 atoms oxygen : . 3 | 8 Of consequence it is similar to sulphuric acid in its composition. The salts of this acid called seleniates, have hitherto been very imperfectly examined. They almost exactly resemble the cor- responding sulphates. But we may distinguish them by the property which they have of detonating when heated to redness with charcoal, and by disengaging chlorine when boiled with muriatic acid. The acid is disengaged from its bases by sul- phuricacid. Selenic and sulphuric acid are isomorphous bodies. 2. Selenious Acid. This is the acid to which Berzelius in his original paper on selenium gave the name of selenic acid. I have described the method of obtaining it and some of its properties in the first volume of this work (p. 290). When the crystals of this acid are exposed to the air, they lose their lustre and adhere to each other, doubtless by absorb- _ ing moisture from the atmosphere, but they do not deliquesce. * See Annals of Philosophy, xiv. 352- + Poggendorf’s Annalen, vii. 70 and 171. 435 Class I,