353 



The Alteration in Specific Gravity of Eucalyptus 

 Oils at Various Temperatures. 



As considerable differences occur in the specific gravities of Eucalyptus oils at 

 various temperatures, it was necessary that some standard be established whereby 

 the several oils might be brought into uniformity. In Sydney the temperature 

 during the summer months is usually high, and the ordinary temperature in the 

 laboratory at that period is often 26 C. To reduce the oils to a standard tem- 

 perature by artificial means was out of the question. It was decided, therefore, 

 to determine the increase or decrease for varying degrees of temperature within 

 ordinary working limits. A special pyknometer was constructed with a fine 

 capillary, standardised at 15 C., and the specific gravity determined at the 

 temperatures given below, the figures being restricted to four places of decimals. 

 The following results were obtained, experimentally, with a Eucalyptus oil rich 

 in cincol, and having a specific gravity 0-9156 at 15 C. : 



At 10 C. specific gravity = 0-9190 



12 C. ,, = 0-9179 



14 C. ,, : 0-9166 



15 C. ,, = 0-9156 



17 C. specific gravity = 0-9141 



19 C. ,, = l o-gi26 



22 C. ,, = 0-9107 



26 C. ,, = 0-9074 



From these results it is seen that 0-00075 is practically the increase between 

 10 and 15 C., and that the same figures represent the decrease between 15 and 

 26 C. Taking the standard specific gravity at 15 C., and calculating either upwards 

 or downwards, as the case maybe, the following figures are obtained, and it is seen 

 that they differ but little from those determined experimentally : 



At 10 C. specific gravity = 

 11 C. 



12 C. 



13 C. 

 14 C. 



15 c. 



16 C. 

 17 C. 

 18 C. 



C. specific gravity = 



C. 



C. 



C. 



C. 



C. 



C. 



0-91260 

 0-91185 

 0-91110 

 0-91035 

 0-90960 

 0-90885 



= 0-90735 



For all practical purposes, therefore, 0-00075 may be taken as the increase 

 or decrease, as the case may be, for Eucalyptus oils within the range of ordinary 

 temperatures in the laboratory, and in this way the specific gravity at 15 C. 

 may be calculated for any Eucalyptus oil, providing the apparatus had been 

 standardised for 15 C. These figures have been repeatedly checked during 

 this research, and have been found to agree very well for all those Eucalyptus 

 oils so tested. It is thus easy to determine the specific gravity of a Eucalyptus 

 oil for 15 C. If, for instance, the specific gravity was found to be 0-9095 and 

 the temperature 21 C., then by adding 0-0045 we obtain 0-9140 as the corrected 

 specific gravity for the particular sample at 15 C. 



Taking advantage of the colder weather in June, determinations were 

 made with two Eucalyptus oils belonging to different classes, in order to test the 

 accuracy of the differences recorded above. A specific gravity bottle holding 50 

 grams of water was employed for the purpose, and the temperature of the oil 

 increased to the desired degree by artificial means. The crude oil of E. Smithii 



