GREY GUM AND ITS ESSENTIAL OIL. 278 
from the young leaves had a specific gravity ‘9169. The specific 
gravity was taken in a delicate Sprengel pyknometer holding 
about ten grams. From the results of the specific gravity deter- 
minations, as well as the rotations, we find that the oils obtained 
from various trees of one species are not constant. 
3. Yield of oil.—The yield of oil from the several trees is not 
constant, ranging from 1°19 per cent. from the leaves of one tree 
to ‘63 per cent. from the young leaves. Leaves and terminal 
branchlets were used in all cases, and therefore the results are not 
strictly comparable, because some might have contained less 
branchlets than others, but not sufficient to account for the 
differences obtained. The yield from the ‘young leaves’ was the 
least obtained, this being contrary to the g lly accepted theory. 
The average yield of oil of nine distillations was °796 per cent., 
and the whole weight of leaves taken was 1377 pounds avoirdupois. 
4. Removal of the terpenes.—The terpenes in these oils, both 
dextro- and levo-rotatory, are largely removed below 172:4° C. 
An oil which had a specific rotation [a], +2°19 when redistilled 
gave the following results :—The fraction (247/) boiling between 
170-4 and 172-4° C. was found to have a specific rotation +3-61° 
while the fraction (60%) boiling between 172-4 and 179-7° O. had 
a specific rotation +1-9° in the same tube. As the distillation 
was stopped at 179-7° C. a portion of the eucalyptol, as well as. 
another body whose rotation was also nil, remained in the still, 
and which would have reduced the rotation in the large fraction. 
We thus see that although the dextro-rotatory terpene is largely 
removed below 172-4° C., yet, it is not possible to remove it by 
the one fractional distillation, and the same remark Bag with 
almost equal force to the levo-rotatory terpene. 
To account for these different terpenes we advance the follow 
ing:—The dextro-rotatory terpene is first formed, as the oil from 
the young leaves had a specific rotation + 4°44°, but as the age oe 
the tree advances this terpene gives place to the levo-rotatory 
form, as the oil obtained from a very fine tree, of a anes age, had 
R—Nov. 3, 1897. 
