Nitric acid, obtained by distilling saltpetre and sulphuric acid, has a powerful effect on inflammable substances. If nitric acid, or in preference, the fuming nitrous acid, be poured on spirit of turpentine, especially if it be old, it will inflame. To succeed, however, in this experiment, a small portion of sulphuric acid is usually added to the nitric acid. As this effect is owing to the facility, with which the acid parts with its oxygen to inflammable bodies, other essential oils, besides turpentine, will have the same effect. If the same acid is poured on finely pulverized charcoal, or on lampblack, combustion will also take place. When oils are used, water as well as carbonic acid is produced, and when charcoal or lampblack, carbonic acid alone. There is also a large quantity of carbon, in the former instance, which remains on the plate, or dish. M. Delametherie (_Journal de Physique_, 1815) has shown, that olive oil may be converted into a substance, resembling, and having many of the properties of, wax, by mixing it with a given proportion of nitric acid. The acid is decomposed, deutoxide of azote is formed, and the oil acquires a hard consistence. A candle made with this artificial wax, he observes, burns with a clear light and without smoke. The experiment with the _glace inflammable_ is on the same principle. Morey (_Silliman's Journal_, vol. ii, p. 121.) states a singular experiment, in which nitre is used; _viz_: If to tallow or linseed oil, a small quantity of saltpetre be added, and the temperature raised to nearly that of the boiling point, the saltpetre appears to be dissolved by the oil; they will _evaporate together_, and the mixture, or the vapour, will burn, _wholly excluded from the atmosphere_. Saltpetre was one of the substances employed by the alchemists. It appears from the memoir of Geoffroy, (_Coll. Academ._ 1722,) that the object of the alchemists was twofold; the transmutation of metals, and particularly what were denominated the _baser_ metals into the precious, which they pretended to effect by a _universal spirit_, the _grand elixir_, the _philosopher's stone_, &c. and the reduction of metals to their _earths_. Alchemy was introduced into Europe by the crusaders, and it is remarkable, that, in the reign of Henry IV, an act was passed to make it felony to transmute metals. Mr. Boyle, aware of its absurdity, suggested the propriety of repealing that act, which was done. One of their powders was composed of nitre, cream of tartar, and sulphur.