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Published online by Cambridge University Press: 17 January 2013
The constitution and properties of the essential oils attracted considerable attention during the earlier period of the investigations in organic chemistry, and several of them have contributed in no small degree to the development of the general doctrines of that department of the science. A majority of these substances, however, may be said to be still almost unknown, all the information we possess regarding them being restricted to a single analysis, made on what was obviously a mixture, or to a few observations of a general and often indefinite character. The complex nature of many essential oils, and the want of experience and easy processes for the separation of their constituents, have hitherto deterred chemists from attempting their minute examination, but the progress of the science has increased our knowledge of the methods of investigating these substances, and renders it important that their true constitution and position in the chemical system be definitely fixed. With this object I have taken up the investigation of Oil of Cajeput; our information regarding which is confined to a single analysis made by Blanchet and Sell, some five and twenty years ago.
page 371 note * Annalen der Pharmacie, vii. 162.
page 371 note † In order to avoid long words I write Cajputene and not Cajeputene, thus rendering the ‘j’ half mute like ‘i.’
page 374 note * Since April last, the time when the present paper was read before the Royal Society, I undertook, at the suggestion of several professional friends, to prepare anew the substances under consideration. The results arrived at now, by repeated combustions and determinations of its vapour density, showing nowhere a difference of much more than one-tenth, if compared respectively with one another, or with those obtained previously, leave really little or no doubt at all about the purity and chemical unity of the substance—however novel, singular, and exceptional it may seem, that the vapour of a body containing one atom of oxygen should condense to four volumes. However, as the substance is easily prepared, the experiment should be repeated by others, and not only with Oil of Cajeput, but with all the bihydrates of the turpentine-radical. Like experiments with bodies of analogous composition will probably increase the number of similar instances. Further remarks as to its reactions, physical qualities, secondary products, and its relation to the Bihydrate of Cajputene, compared with which it might prove to be an analogous ether, I will endeavour to give in a subsequent paper.