The chemistry of essential oils and artificial perfumes / by Ernest J. Parry.

  • Parry, Ernest J. (Ernest John)
Date:
1908
Catalogue details

Licence: In copyright

Credit: The chemistry of essential oils and artificial perfumes / by Ernest J. Parry. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    are well shaken at intervals during a fortnight. The crystals formed, consisting of the compound of thujone with the sodium bisulphite, are separated, washed with alcohol-ether and pressed. On treatment with caustic soda solution, the thujone, amounting to over 40 per cent, of the oil used, separates, and can be distilled with steam. The hitherto unanswered question whether the chemi- cally identical thujones isolated from various essential oils are also physically identical, or whether they are physically isomeric, has now been decided by Wallach in the last-named sense. He has succeeded in establishing the presence of two and possibly of three thujones, although with regard to the third the more probable view is, that it represents a mixture of the other two. His examination has moreover proved that thuja oil contains essentially a-thujone, and oil of tansy essentially /3-thujone. Wormwood oil is very rich in /3- thujone, but also contains some of the a-compound. Oils of artemisia and sage contain mixtures of a- and /3- thujones. The formation of the semicarbazones and their fractional crystallisation from methyl alcohol afford means for the separation and identification of the isomers. a-thujone is laevo-rotatory, and yields two semicarbazones, one dextro-rotatory, melting at 186° to 188°, and one, also dextro-rotatory, of the indistinct melting point 110°. Pure a-thujone has the following properties : boiling point, 200° to 201°; specific gravity, 0-912; nd22o 1-4503; [a]„ -10-23°. a-thujone is partially converted into /3-thujone when heated with alcoholic potash solution, formic acid, or alcoholic sul- phuric acid. The last-named then effects a further conver- sion into isothujone (q.v.). /3-thujone is dextro-rotatory, but is not the optical anti- pode of a-thujone. The semicarbazone exists in a labile dextro-rotatory form of the melting point 174° to 176°, which readily passes over into the second form, melting at 170° to