212 ODOROGRAPHIA. 



6. Strong caustic potash solution has no action on pure menthol. 



The sp. gr. of English oil of peppermint is recorded by Messrs. 

 Schimmel* as being 0-905 at 10^ C, 0-900 at 15^ C, and 0-898 at 

 20^ C. ; and that of the American 0-906, 0-903 and 0-901 at the 

 same respective temperatures, t 



Investigations made by Mr. A. M. Todd, a large distiller of oil 

 of peppermint in Michigan, resulted in slightly different figures. 

 In a paper read by him at a meeting of the American Pharma- 

 ceutical Association in 1886 he states : — " The difficulty which 

 scientific men seem to have experienced in establishing accurate 

 tests for the purity of essential oils has been that they could not 

 conveniently obtain the plants from which they themselves could 

 distil the specimens used in their investigations ; and, while 

 undoubtedly every possible precaution was taken, the result show^s 

 that they have in many instances operated upon impure samples, 

 and although pure specimens undoubtedly were in some instances 

 received, yet they had in many cases no positive knowledge, ^^e?' se, 

 which were pure and which were impure ; hence too great a range 

 of differences has been allowed in physical characteristics and 

 chemical reactions.^ 



In correspondence with some well-known chemists, they gave it 

 as their opinion that a wide range of specific gravity, &c., might 



* Bericht, April, 1887. 



t The age of these samples tested is not stated, neither is it stated if any 

 resin originally contained in them had been rectified out before testing. 

 At a meeting of the British Pharmaceutical Conference held 24th August, 1880, 

 it was pointed out by Mr, Umney that crude Mitchani oil of peppermint always 

 contains a large amount of resinous principle, and its presence is owing to the 

 rough way in which the oil is manufactured, parts of the charge of plant in the 

 still being charred ; thus empyreumatic matter is driven over, and a large 

 quantity of resinous matter is consequently present in the oil. He considered 

 that no specimen of English manufacture could be considered pure unless it had 

 been rectified with water, and even then a very small quantity of the resinous 

 principle would be present. 



X In the discussion on a paper *• on the Constituents of Peppermint oil " by 

 Professor Flilkiger and Dr. Power, read at a meeting of the British Pharma- 

 ceutical Conference in August, 1880, it was observed by a Member of the 

 Conference that investigation showed "that adulteration varied over a large 

 number of specimens, and it was difficult to determine what could be relied 

 upon unless the experinientor were present and saw the oil made, or made it 

 hinvself. It seemed as difficult to obtain pure peppermint oil as genuine port 

 wine, which, it was said, could only be secured by going to Portugal and buying 

 a cask, and then sitting on it all the way home." 



