156 E. I. Roseiihlurii: 



The density and refractive index of the terpineol indicate that 

 it is mainly the isomer of M. Pt. 350-.'36o C, Avhile the high den- 

 sity and diminished rotation of the d-limonene point to some 

 modification having occurred since it was originally prepared by 

 Kahlbaum. 



Although the uncertain purity which is inherent to the terpenes 

 renders these results less valuable from the point of view of physico- 

 chemical theory, they may none the less be regarded as standards 

 bv workers in the fascinating field of Essential Oils. 



(1) The Density. 



The densities were measured at ten degree intervals between 10° 

 and 60O by means of a pyknometer holding about 6 c.c, and a 

 bath, which could be maintained at any required temperature, 

 while a measurement was in progress. Incidental errors due to 

 expansion of the glass of the pyknometer, etc., were eliminated 

 by taking a series of pyknometer values for distilled water over 

 the temperature range, calculating the specific gravity from these, 

 and then deriving the density as referred to water at 4° (\ from 

 the tables of the density of water. 



These densities at ten-degree intervals are shown in the accompanying 

 table. 



It will be observed that, while the coetficients of expansion are 

 in all cases close together, they fell into two groups, the oxy- 

 genated substances cineol, safrol and eugenol expanding to a 

 greater degree than the hydrocarbons. 



Citral, the only straight chain terpene, and terpineol, are ex- 

 ceptional. The relation of temperature to density is strictly linear 

 except in the case of the ever-exceptional 1-phcllandrene, whore a 

 slight divergence is shown. 



