Source, Etc

Camphor is a crystalline substance contained in the volatile oil of the camphor tree, Cinnamomum Camphora, Linne (N.O. Laurineoe), a large tree indigenous to the island of Formosa, and to Japan and China. It is cultivated also in Ceylon, the Federated Malay States, India, Burma, Java, East and West Africa, California, etc. The leaf, petiole, bark, wood, and pith of the tree contain numerous oil cells. In these a volatile oil is secreted which, by oxidation, yields camphor. It is also found in the solid state in cavities in the trunk, probably as the result of slow volatilisation and oxidation of the oil. The yield of oil varies from 2 to 6 per cent. and that of the camphor from 0.2 to 3 per cent., old trunks containing the most.

Production

Camphor is usually obtained by passing a current of steam through the chipped wood of the trunk and root, a primitive form of still being used for the purpose. From the pasty mixture of solid camphor and liquid volatile oil obtained the camphor is separated by pressing. The oil is exported under the name of camphor oil; by fractional distillation is yields light camphor oil (boiling-point, 175° to 200°) consisting of pinene, phellandrene, cineol and dipentene, and heavy camphor oil (boiling-point 200° to 275°) containing safrol and eugenol, and utilised for the production of the former on the large scale. The crude camphor is purified by mixing it with lime, charcoal, etc, and subliming it in large glass flasks (bomboloes); the camphor sublimes in the upper part of the flask and is obtained in the form of a thick ring by cracking the flask. It may also be sublimed into flat cakes or, by passing the vapour into large cooled chambers, into small crystals (flowers of camphor) which may be pressed into rectangular cakes by hydraulic pressure.

Description

Camphor occurs in small, colourless crystals or in translucent, fibrous or crystalline masses with a characteristic penetrating and pungent, bitterish taste, followed by a sensation of cold. It burns readily with a bright, smoky flame, and is volatile at ordinary temperatures. It is a ketone, yielding isoborneol by reduction and camphoric acid by oxidation. With vanillin-hydrochloric acid it gives a reddish blue or bluish green colour which appears to be due to impurities derived from the plant during the distillation.

Uses

Camphor is used externally as a mild rubefacient, internally as a carminative and antiseptic.

Varieties

Synthetic camphor is obtained from pinene by converting it into pinene hydrochloride from which isobornyl acetate and isoborneol are successively prepared; isoborneol is then converted by reduction into camphor. Synthetic camphor may be distinguished from natural camphor by its optical inactivity (natural camphor is dextrorotatory) and by its not yielding the colour reaction with vanillin-hydrochloric acid. It can be resolved into dextro- and laevo-camphor.

Borneo camphor is obtained from Dryobalanops aromatica, Gaertner (N.O. Dipterocarpeoe), Borneo. The camphor is secreted normally in ducts in the pith, but similar ducts are probably formed pathologically in the young wood. Cavities filled with the camphor occur in the pith and from these the camphor is scraped out. It consists almost entirely of dextro-borneol. It is employed in China and Japan for embalming and also for various religious ceremonies.

Ngai camphor is obtained from Blumea balsamifera, de Candolle (N.O. Compositae), Burma, by distillation of the leaves. It consists of laevo-borneol and is used in China as a medicine and for religious ceremonies.