208 ODOROGRAPHIA. 



consisting of about five per cent, of the oil, are removed by 

 fractional distillation under reduced pressure, the menthol can be 

 crystallised out from the heavy portion remaining, by submitting 

 it to a temperature of about — lO'^ C. The solidification is 

 accelerated by dropping a few crystals of menthol into the liquid 

 when the thermometer marks the point of congelation. 



The liquid portion of Mitcham peppermint oil, has been found* 

 to consist simply of isomeric and polymeric terpenes, having an 

 odour entirely distinct from peppermint, somewhat reminding of 

 lemon oil, though corresponding more nearly to that of freshly 

 distilled turpentine oil. 



If the light oil and the menthol be both fractionated off from 

 the crude oil, there will be found in the still a resinous mass, 

 almost free from odour. This appears to be partly formed during 

 the process of distillation, and amounts to about 10 per cent, of 

 the original oil. 



The liquid portion of Japanese peppermint oil has been found 

 by Beckett & Wrightf to contain a small amount of a substance 

 isomeric with borneol. 



Menthol is very soluble in alcohol, ethers, chloroform, carbon- 

 disulphide and most oils, but is more soluble in oil of peppermint 

 than in any other. It has a sp. gr. of 0-890 and small particles 

 gyrate on the surface of water like camphor. Several compounds 

 of menthol have been obtained, the acetate, formed by heating 

 menthol with glacial acetic acid, being a light, oil-like body without 

 colour. By substituting butyric for acetic acid, butyrate of 

 menthol is obtained. 



Tlie variety of menthol obtained in Michigan from the oil of 

 Mentha pij^erita, is termed " pipmenthol," in order to distinguish 

 it from the Japanese article. It has a distinct odour of peppermint; 

 Japanese menthol has that odour but slightly. 



]\Ienthol has been used by the Japanese for about 200 years, 

 and is known ];)y them as " Hakka-ne-sei " or " Hakka-no-Hari." 

 Previous to the late change in the social system of Japan, the 

 native gentlemen were accustomed to carry attached to their girdle 

 a medicine-box, which contained, among other things, a com- 



* Fliickiger & Power, in a paper read at the British Pharmaceutical 

 Conference, August, 188Q. 



t Journ. Chem. Soc, 1876, p. 3. 



