Fhysicat Chemistry of Essential Oils. 155 



Summary. 



Simple mixtures of two terpens compounds follow the " Mix- 

 ture Law" quite closely. The divergences, at any time small, are 

 eliminated by the use of the " Molar Fraction Fox-mula." 



For such mixtures the proportions of the constituents can be 

 calculated from the properties of the mixture, but whex'e one con- 

 stituent is niistal)le. as in phellandrene oils, such deductions are 

 unreliable. 



These measurements w^ere made in the research laboratories of 

 the University of Melbourne, for the use of which we have to thank 

 Professor Masson. 



Our thanks are also due to Professor Osborne for the use of his 

 polarimeter. and especially to Mr. H. G. Smith for his generous 

 gift of pinene eucalyptus oils. 



Part II. — 7%e Physical Constants of some Terpenes and oxygenated 

 derivatives thereof, and their variation with temperature. 



E. IVAN ROSEN BLUM, M.Sc. 



(Comnmnicated by VV. Heber Green, D.Sc). 



[Read 9th July, 1914). 



Some measurements which had been made in the course of the 

 last paper, and the fac-t that he had on hand samples of a number 

 of terpenes prepared for that research, led one of the authors to 

 make a so-ies of measurements on the influence of temperature 

 change on the three chief physical constants of terpenes — Density, 

 Kefractive Index, and Rotation. 



The terpenes employed are, in the main, those whose purifica- 

 tion has been described in the joint paper ; the others were as sup- 

 plied by Merck and Kahlbaum, and, with two exceptions, their 

 purity as indicated by their constants and by the usual tests was 

 such as to render it unnecessary to submit them to the somewhat 

 uncertain processes involved in further purification. 



