GREY GUM AND ITS ESSENTIAL OIL. 275 
We find that the specific gravity of the oil is no indication of 
the amount of eucalyptol present, as the oil giving the highest 
specific gravity ‘9205 gave only 51°6 per cent. of eucalyptol, while 
an oil whose specific gravity was 9164 gave 64:5 per cent. 
eucalyptol. We regret that our researches on this oil prevent our 
endorsing the applicability of the ingenious method for the deter- 
mination of eucalyptol in an oil by taking advantage of its physical 
determinations as worked out by Mr. W. Percy Wilkinson." 
It is most probable that the Eucalyptus oils are divisible into 
groups, the members of which contain certain specific constituents, 
other than eucalyptol in varying quantities, the physical constants 
of which are not yet worked out. If eucalyptol and one terpene 
were the only consituents present in these oils, their investigation 
would be much simplified. The fraction boiling between 182:8 
and 193° C., and which varies from two to seven per cent. of the 
original oil, contains only a small quantity of eucalyptol,? 28 per 
cent.; it has no action on light, and probably consists largely of 
an ester partly decomposed by distillation, as an odour of acetic 
acid is readily detected. It will be further investigated. 
[t appears to us at present not to be advantageous to rectify 
this oil beyond 183° ©, as the fraction between this and 193° C. 
would tend to lower the eucalyptol content of the large fraction. 
The determinations of the eucalyptol were made by the phosphoric 
acid method, a powerful letter press being used to remove the © 
adhering terpenes etc. Most of the determinations were made in 
duplicate, and the more important ones in triplicate, the mean of 
these results being given. 
Determinations under exactly the same conditions were made 
on a sample of the oil of #. globulus, kindly sent to the Museum 
by the Tasmanian Eucalyptus Oil Co., the manufacturers of the 
“Platypus Brand.” Three determinations of eucalyptol on this 
oil gave 49:6, 49-8, and 49-9 per cent., while the lowest determin- 
1 Proe. Roy. Soc: Vic: Vol. v1., New Series, page 195. 
2 This same fraction of E. globulus is principally eucalyptol. 
