Dr. Kane on the Composition of certain Essential Oils. 



141 



Upon the whole it is evident, that we cannot consider the nature of the oil 

 and stearopten of peppermint as being absolutely determined ; at the same time, 

 I conceive myself justified in placing some confidence in my results, from their 

 agreement, and the care with which the substance had been purified. 



IV. OIL OF PENNYROYAL. — (MENTHA PULEGHIUm) 



The oil of pennyroyal is stated by Mr. Brande to have a specific gravity of 

 0.939- I could not obtain it in commerce with a specific gravity higher than 

 0.9271. I consider, however, the specimens having that specific gravity as 

 being pure, and that a higher density arises from dissolved stearopten. The 

 oil of 0.9271 having been rectified, left but little solid matter ; and the pure oil, 

 after distillation, had a specific gravity of 0.9255. Its boiling point could not be 

 obtained quite constant, fluctuating between 360° and 370° Fahr. At the end 

 of this paper a few remarks on the boiling points of these oils will be found. It 

 was analyzed as follows : 



A. Material =: 0.3607 gramme gave 



Water = 0.353 



Carbonic acid = 1.020 



B. Material = 0.3014 gramme gave 



Water = 0.297 



Carbonic acid = 0.861 

 Hence per cent. 



100.0 



77.4 100.00 



This result is exceedingly remarkable, as from it follows that oil of penny- 



