MINT. 207 



that the oil extracted from the plants near Utrecht deposited 

 crystals of C amphora Euro-pea Mentha^ Plpcritides* The Japanese 

 and Chinese oils contain this substance in much larger quantities 

 than either the English or the American oils, and frequently occur 

 in the form of a crystalline mass saturated with liquid hydro- 

 carbons. 



This peppermint camphor was mistaken for ordinary camphor 

 until Dumasf and Blanchard Sell;[: detemined its composition, and 

 Walter§ fixed its molecular formula by a determination of its 

 vapour density, which was found to be 5-62. It was first proved 

 by demonstration to be an alcohol by Oppenheim|l by the 

 formation of several compound ethers, and it has been shown by 

 Beckett and Alder AVrightV to be connected both with the paraffin 

 series and the benzene series, inasmuch as by the action of dehydrat- 

 ing agents (decomposition by heating with phosphorus pentachloride 

 or zinc chloride) it is easily converted into mcnthene, C^oH^g, a 

 dextro-rotatory liquid, which smells like cymene, boils at 167'^,and, 

 by the action of bromine, combines to form tetrabromdecane, 

 which is converted into cymene by heating and distilling the 

 product with sodium. 



Menthol, when purified by repeated crystallisation, forms into 

 large prisms which have somewhat the appearance of magnesium 

 sulphate. It remains solid at ordinary temperatures, melts at 

 420-2 C.,** boils at 212^ C, and is laevo-rotatory. Commercial 

 menthols melt at from 37°-7 to 42^*2 C, the melting point 

 depending on the freedom of the menthol from the hydrocarbon 

 constituents of the essential oil ; a very small percentage of such 

 hydrocarbons lowering the melting point considerably. It has 

 been shown by Trimblef f that the presence of a very small quantity 

 of hydrocarbon is sufficient to hold the menthol in solution and 

 prevent it from crystallising out, but if these hydrocarbons, 



* Fliickiger, "Pharmakognosie," p. 6S6. 

 t Ann. Chem. Pharm., vi., p. 252. 

 X Ibid., vi., p. 293. 

 § Ibid., xxxii., p. 288. 



II Ibid., cxx., p. 350, and cxxx., p. 176 ; Comptes rendus, liii., p. 379 and 

 483, and Jahresbericht der Chemie, 1861, p. 683; Journ. Chem. Soc, xv., p. 24. 

 *" Year Book of Pharmacy, 1875, p. 605. 

 ** Beckett «Iv: Wright, Journ. Chem. Soc, 1876, i., p. 1. 

 ft Pharmaceutical Record, 1885, pp. 291 and 312. 



