284 EUCAL YPTUS. 



The Eucalyptus oil might be described as a ' ' compound 

 oil," some of the constituents of which volatilize at various 

 temperatures with a residue that cannot be volatilized except 

 by "destructive distillation." 



The Eucalyptus oils of commerce are obtained from 

 the leaves of the different varieties of Eucalyptus, by dis- 

 tillation in an ordinary still and condensing coil. The best 

 results were obtained when the steam pressure in the boiler 

 was maintained at not less than eighty pounds, and when 

 the leaves were put in the still loosely in such a way that 

 they could not pack down. Repeated trials show that by 

 crowding the still a loss of between twenty-five and twenty - 

 eight per cent, resulted; i. e., less oil would come over 

 when the leaves were packed in the still, or allowed by 

 their own weight to pack down. This packing of the 

 leaves can be avoided by putting in a layer of leaves, say, 

 one foot in thickness, then a porous frame or lattice rack 

 made to rest on the sides of the still or cage. On this 

 frame or rack another layer of leaves could be placed, and 

 on these another frame, and so on, until the cage or still 

 was filled. The reason for this want of recovering all the 

 oil in a closely packed still will be readily understood when 

 it is considered that the oils are non-volatile at the tem- 

 perature of the steam within the still, but are taken up 

 mechanically by the steam and carried over with it. 

 The pressure in the still never exceeded fifteen pounds, 

 therefore the heat could not have exceeded 248 degrees, F., 

 a temperature at which only a very small portion of 

 oil will volatilize. 



The following table will show the amounts of oil yielded 

 by some 26 varieties of Eucalyptus, together with their 

 specific gravities and colors : 



