CAMPHOR is a principle of vegeta bles, which, in many of its properties, re sembles the volatile oils. Like them, it is odorous, pungent, volatile, inflamma• ble, sparingly soluble in water, and abun dantly soluble in alcohol. It differs from them principally in its concrete form, in its peculiar odour, in its relation to the acids and alkalies, and the results of its decomposition by heat. Camphor is a principle contained in many vegetables, especially the aromatic plants, and even those of our own country, as pepper mint, rosemary, marjoram, and others ; it appears to be volatilized in combina tion with their essential oil in the pro cess of distillation, and, when these are long kept, is deposited in a crystalline form.
The camphor of commerce is procur ed, however, from a particular plant, the laurus camphora, a native of the east of Asia. It exists ready formed in the wood of this tree, can be seen interspersed through it in vesicles, and can be picked out. It then forms what has been named native camphor. It is usually procured, however, by the process of sublimation. The wood of the stem and branches, cut into small billets, is exposed with a little water to a moderate heat, in a kind of alembic, to the head of which is adapted a capital, in which straw is put. The cam phor is volatilized, and attaches itself to the straw. It is a little impure, but is pu rified in Europe by a second sublimation. The camphor of commerce, from its mode of preparation, is in the form of large se mi-spherical cakes : when broken, it ap pears in fragments of a texture somewhat striated, having a degree of ductility, in consequence of which it can be com pressed, and is not easily reduced to powder ; of a white colour, and semi transparent : a little unctuous to the feel ; having a very strong, peculiar, and rather fragrant odour, and a taste which is pungent and bitter. It is also suscep tible of crystallization : when slowly sub limed, or when slowly precipitated from its solution in water by the allusion of al, clahol, it appears in the form of acicular prisms.
Camphor, though a concrete substance, is even more volatile than the essential oils. It evaporates quickly at the com mon temperature of the atmosphere, losing in weight, and an •angular frag ment ; and at a tem perature between 100 and 150, it sub-' limes in close vessels unchanged. It is highly inflammable, kindles very readily, and burns with the emission of much light, and with a dense black smoke, which condenses into a smooth light char coal. Carbonic acid gas is produced, and a portion of the peculiar acid which has been named camphoric acid.
Camphor is very sparingly soluble in water. When triturated with it, it mere ly communicates its smell and taste to the water, which remains odorous, and some what pungent, even when filtrated ; but no appreciable quantity is dissolved. A phenomenon which has excited some at tention is presented, when pieces of cam phor are placed on the surface of pure water. They soon begin to move with rapidity, and while moving dissolve, the solution taking place nt the line where the water and the air are in contact; as is proved by immersing a cylinder of camphor in water part of its length : it becomes excavated, and at length is cut through, exactly on a level with the sur face of the water.
Camphor is abundantly soluble in alco hol : the solution is immediately decom posed, and the camphor precipitated in the form of a white powder, by the allu sion of water ; but if the water be very slowly added, and merely in such a quan tity as to weaken the affinity of the alco hol to the camphor, the latter, in sepa rating, presents a deutritic crystallization. It is also soluble in expressed and essen. tial oils. The alkalies do not dissolve camphor, or produce in it any sensible change. Of the earths, magnesia appears to exert some action on it, as, when they are triturated together, the camphor is reduced to a smooth impalpable powder, which is easily diffused in water. The action of the stronger acids on camphor Is peculiar, and presents some singular results.