The class of acids is characterised by very distinct properties. They all change blue vegetable infusions to a red colour: they are all more or less sour to the taste; and have a general tendency to combine with the earths, alkalies, and metallic oxyds.
You have, I believe, a clear idea of the nomenclature by which the base (or radical) of the acid, and the various degrees of acidification, are expressed?
EMILY.
Yes, I think so; the acid is distinguished by the name of its base, and its degree of oxydation, that is, the quantity of oxygen it contains, by the termination of that name in ous or ic; thus sulphureous acid is that formed by the smallest proportion of oxygen combined with sulphur; sulphuric acid that which results from the combination of sulphur with the greatest quantity of oxygen.
MRS. B.
A still greater latitude may, in many cases, be allowed to the proportions of oxygen than can be combined with acidifiable radicals; for several of these radicals are susceptible of uniting with a quantity of oxygen so small as to be insufficient to give them the properties of acids; in these cases, therefore, they are converted into oxyds. Such is sulphur, which by exposure to the atmosphere with a degree of heat inadequate to produce inflammation, absorbs a small proportion of oxygen, which colours it red or brown. This, therefore, is the first degree of oxygenation of sulphur; the 2d converts it into sulphurous acid; the 3d into the sulphuric acid; and 4thly, if it was found capable of combining with a still larger proportion of oxygen, it would then be termed super-oxygenated sulphuric acid.
EMILY.
Are these various degrees of oxygenation common to all the acids?
MRS. B.
No; they vary much in this respect: some are susceptible of only one degree of oxygenation; others, of two, or three; there are but very few that will admit of more.