[346]. The only mineral substances in which this acid has been found is the Fer Azuré of Haiiy, and a new substance which is found accompanying Welsh Culm, and of which I have given an account in the first volume of the Transactions of the Royal Geological Society of Cornwall, although in this latter instance it is probably a product, not an educt.
[347]. The following is the chemical reasoning upon which this process is founded. “The prime equivalent of prussic acid is exactly one-eighth of that of the mercurial peroxide. But as the prussiate of mercury consists of two primes of acid to one of base, or is in its dry crystalline state a By-cyanide, we have the relation of one to four in the formation of that salt, when we act on the peroxide with cold prussic acid.” Hence is derived the above simple rule of analysis. (Journal of Science and the Arts.) Upon the same principle it has been already stated, that the quantity of real acetic acid, in any given sample of distilled vinegar may be discovered by the test of carbonate of lime, see Acid. Acetic. Fort. They furnish beautiful illustrations of the practical importance of the doctrine of Definite Proportions.
[348]. This offers a striking example of the confusion produced by the constant changes in chemical nomenclature; in the former editions of this work, the term Hydro was prefixed to Muriatic Acid, as an epithet expressive of the presence of water, whereas the same word is now used to denote the existence of Hydrogen as one of its elements.
[349]. Dr. Powell directs only two parts of acid; but this is evidently too little, for it appears by Dr. Wollaston’s scale, that 3 parts of salt require 2½ of oil of vitriol for their decomposition; and in addition to this, the oxide of manganese will require a farther addition to convert it into a sulphate.
[350]. As Chlorine is by pressure condensable into a liquid, tubes containing a small quantity of it, and hermetically sealed, might be very usefully employed for this purpose, since by breaking off the extremity, the chlorine would instantly assume the gaseous state, and diffuse itself through the apartment.
[351]. There is a curious illustration of this fact in the German “Ephemerides;” the case of a person is described who had taken so much Elixir of Vitriol that his keys were rusted in his pocket, by the transudation of the acid through his skin!
[352]. Nitric acid may be considered as one of the most efficient agents in our possession for exciting prompt vesication. For this purpose, we believe it was first used in the epidemic Cholera of the East Indies, and the success which attended it in that fatal disorder suggested its application in a variety of other diseases. The mode of using it is to rub the surface intended to be vesicated, with the pure acid, and as soon as pain is produced, to neutralize the acid by washing the part with a solution of salt of tartar. If the object is to continue the irritation, a common blister may be laid upon the part. Ed.
[353]. Nitrous acid gas is a combination of nitrous gas and oxygen.
[354]. Elixir of Vitriol. The preparation sold under this name is the Acid: Sulph: Aromat: E. and is imperfectly ætherial in its nature. It is a grateful medicine. A spurious article is often sold for it, which is nothing but the diluted acid, coloured by the addition of a tincture.
I will take this occasion to state, that the term Elixir is of Arabian origin, viz. Elechschir, or Elikscir, i. e. an Essence, or pure mass without any dregs.