MIXT. 217 



of pure resin ; of course by applying the iodine test, such oil will 

 explode at once. Mitcham oil is nearly colourless, sometimes 

 however, it has a natural very pale greenish tinge, which is often 

 imitated by the addition of chlorophyl. Old, dark-coloured oils 

 are commonly bleached by exposure to the light, to the probable 

 destruction of a portion of their other properties. 



During a trial which took place in Wayne County, concerning 

 fraudulent oil of peppermint, it was shown that the oil had not 

 only been deprived of its menthol, but had been largely adulterated 

 with oil of camphor. The removal of the menthol may be detected 

 by first fractionating off the light oil, then subjecting the residue 

 to a low temperature (about — 12^ F.), when the menthol should 

 freeze out. It can also be ascertained by the aid of the polariscopcj 

 menthol being strongly h^evogyre, and oil of camphor dextrogyre to 

 about an equal degree. 



Large quantities of American oil of peppermint have frequently 

 been imported into Canada which were found on examination to be 

 adulterated with castor oil and alcohol. On one occasion a parcel 

 of 551b. was submitted to distillation ; ISlbs. of oil of peppermint 

 of good quality were separated from the distillate and the residue 

 in the still, weighing 211bs., was found to be castor oiL The 

 difference between the sum of these two weights and the original 

 quantity represented the amount of alcohol present. A mixture 

 of these constituents in the above proportions yielded a clear and 

 presentable oil, strongly resembling the genuine article. Its 

 density was slightly lower (-894 at 60° F.), its reactions with iodine 

 were precisely similar, and it dissol\^ed perfectly in rectified spirit. 

 The presence of the fixed oil may, however, be detected by the 

 characteristic stain it leaves upon paper, and that of the alcohol by 

 agitation with an equal volume of water, when a milky emulsion 

 will be produced. 



Menthone, C\o H^g 0- This Ketone is formed by heating 

 menthol with sulphuric acid and potassium bichromate.* It is a 

 mobile liquid which smells of peppermint and boils at 206° C. 

 When its solution in petroleum is heated with sodium, and a current 

 of carbon dioxide passed through the mixture, the product yields 

 menthol on decomposition with water. The latter substance 



* Moriya, Journ. Chem. JSoc, 1881, p. 77. 



