Note 333 — PHARMACOLOGIA.

It had been long known that by the destructive distillation of any kind of wood, an acid is obtained, which was formerly considered of a distinct and peculiar nature, and termed Acid Spirit of Wood, and afterwards Pyroligneous Acid. Glauber appears to have been the first chemist who was aware of its true nature, for he speaks of it as the “Vinegar of Wood.” It was however reserved for Fourcroy and Vauquelin to demonstrate its composition by experiment, and they have accordingly proved beyond doubt that it is merely the Acetic acid, contaminated with Empyreumatic oil and Bitumen. The address of modern chemists has at length enabled them to get rid of every trace of these latter ingredients, and to furnish an acid perfectly devoid of any foreign flavour. The crude pyroligneous acid, as it is first received, is rectified by a second distillation in a copper still, in the body of which about 20 gallons of viscid tarry matter are left from every 100. It has now become a transparent brown vinegar, having a considerable empyreuma; it is then redistilled and saturated with quick-lime, and the liquid acetate is evaporated to dryness and submitted to gentle torrefaction, in order to dissipate the empyreumatic matter, and lastly the calcareous salt is decomposed by sulphuric acid, when a pure, perfectly colourless, and grateful vinegar rises in distillation.