February 24, 1872.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
687 
ESSENTIAL OILS.* 
BY J. H. GLADSTONE, BH.D., F.R.S. 
Part II. 
Eight years ago I communicated a paper on essential 
oils to the Chemical Society, and in concluding it I pro¬ 
mised a further communication, with experiments on the 
oxidized oils, and a fuller account of the chemical and 
physical history of some of the hydrocarbons. Shortly 
after the paper was printed, a series of unforeseen events 
took me almost wholly away from my laboratory; other 
scientific inquiries then engrossed my thoughts ; and so 
the research on these essential oils was long laid aside. 
Now, however, I will endeavour to fulfil my promise, 
though not to carry out my whole design. 
Before entering on any new observations, I wish to 
jefer to some criticisms on my paper which Mr. Daniel 
Hanbury kindly sent me. They relate to the plants 
from which the oils are derived; and, as I know little of 
the subject myself, I will just place his statements against 
those of Mr. Piesse, on whose authority each of the con¬ 
troverted names was given. 
Oil of calamus is distilled, not from Calamus aroma- 
ticus , hut from the rhizome of Acorns Calamus. 
Indian geranium oil is yielded by Andropogon Pach- 
.nodes. 
The wild thyme of our heaths, Thymus Serpyllum , 
gives an essential oil, hut the oil of thyme of commerce 
as from Thymus vulgaris. 
During the past spring I was furnished by Mr. Piesse 
with specimens of some rare essential oils, not previ¬ 
ously examined—those of citron, lign aloes, pimento, 
and vitivert. 
The following were the determinations of the specific 
gravity and refraction of these oils as they came into my 
■hands:— 
Crude Oils. 
Specific 
Gravity. 
Temp. 
Cent. 
Refractive Indices. 
A. 
1). 
H. 
Citron. . . 
0*8914 
10° 
1*4729 
1*4797 
1*5011 P 
Lign Aloes . 
0*8702 
18° 
1*4620 
1*4679 
Pimento . . 
1*0374 
10° 
1*5229 
1*5325 
1*5660 P 
Vitivert . . 
1*0070 
19*5° 
1*5147 
1*5218 
Citron. —This oil was obtained from the leaves of the 
lemon, Citrus Limonum. It was slightly yellow. It 
began to boil at 155° C., but the hulk consisted of a 
liquid having the boiling-point 166°-168°; the specific 
.gravity 0*8549 at 19*5°; the refractive index for A, 
1*4680 ; and the dispersion 0*273. Its odour resembled 
that of lemon, and it was probably identical with the 
hydrocarbon found in other parts of the same plant. 
Lign Aloes .—This is a colourless oil, with a charac¬ 
teristic pleasant odour, believed to be obtained from the 
wood of a large tree that grows in Mexico.fi The prin¬ 
cipal part distils over at somewhere about 200° ; but it 
seemed impossible by fractional distillation, even with 
the aid of sodium, to obtain a body of a fixed boiling- 
point. The specific gravity and optical properties of 
the best rectified oil are given later on in this paper; 
they will be found to resemble closely the properties of 
citronellole, suggesting the idea that the principal con¬ 
stituent may also have the composition C 10 H 16 O. 
Pimento .'—This pungent oil is derived from the seeds 
-of Myrtus Pimento. It began to boil at about 197°, and 
the thermometer rose gradually to 242°, about which tem¬ 
perature the greater portion passed into the receiver. 
The first portion consists partly of an oil insoluble in 
potash; the second is wholly dissolved by an alkali. 
When rectified, though perhaps not quite pure, it was 
* Read before the Chemical Society, Dec. 7, 1871 ( Journ. 
> Chem. Soc. [2] x. i.). 
fi The Lign aloes of the sacred Scriptures is supposed to 
foe the Aquilaria Agallochum of Northern India. 
found to have the boiling-point 243°; specific gravity at 
12*5°, 1*0436; refractive index for A 1*5281; and dis¬ 
persion about 0*416. Its odour was that of eugenic acid, 
and like that body it was freely soluble in potash, giving 
two salts, of which that which contains the larger pro¬ 
portion of acid will separate from a moderately strong 
solution in crystalline masses. As the physical pro¬ 
perties mentioned above accord sufficiently well with 
those previously determined for eugenic acid,* there can 
scarcely be a doubt that oil of pimento is substantially 
the same as oil of cloves, while each contains a small 
proportion of a hydrocarbon, to which is due the difference 
of their odours.fi 
Vitivert. —The crude oil was very viscid, of a dark 
brown colour, with an odour suggesting both sandal¬ 
wood and patchouli. On repeated distillations it was 
found to consist mainly of a liquid boiling at 280°-283°, 
but the action of sodium showed that this was a mixture 
of two bodies, the one decomposable and the other un¬ 
alterable by that metal. The rectified oils were of a 
brownish-green colour on being freshly distilled, and 
changed to a truer green shortly afterwards—a circum¬ 
stance which I have not observed in any other case. 
An examination of the hydrocarbon is given below, and 
confirms the close resemblance of this oil to those of 
cedar and sandal wood. 
The Hydrocarbons. 
These are all of the composition C 10 H 16 , or a multiple 
of that. In the previous paper I described several new 
ones, of which I analysed eight. No names were given 
them beyond that of the oil from which they were ob¬ 
tained, but now, in accordance with the usual practice, 
I would suggest the following :— 
Hydrocarbon from Bay.Laurylene. 
„ ,, Calamus.Calamene. 
„ „ Dill ...... Anethene. 
,, „ Elder ...... Sambucene. 
,, ,, Eucalyptus amygdalina Eucalyptene. 
,, ,, Myrtie.Myrtene. 
„ „ Nutmeg.Myristicene. 
„ „ Rosewood .... Rhodiene. 
Polymeric Groups. 
When treating of the hydrocarbons of the essential 
oils in my previous paper, I distinguished between three 
polymeric groups, to which were assigned the formulae 
C 10 H 16 , C 15 H 24 , and C 20 H 3 . 2 . The first group were said 
to comprise the great mass of these hydrocarbons—tur¬ 
pentine, orange, caraway, nutmeg, anise, thyme, myrtle, 
and twenty others; the second, those derived from cloves, 
rosewood, cubebs, calamus, cascarilla and patchouli; 
while the third group was represented by colophene. 
That colophene also has its isomerides is rendered 
probable by the descriptions given of paracajputene, 
and of the substances from other sources which have 
been named colophene, but which are probably not iden¬ 
tical with it. 
If there is this distinction, the vapour-densities of 
members of the three groups should be different. Now 
the densities of oil of turpentine, pepper, juniper, elemi, 
lemon and orange, together with gaultherylene, vale- 
rene, citrene, terebene, carvene and caoutchene had been 
determined by various experimenters to be about, though 
generally a little above, the theoretical density lor 
C 10 H 16 , viz. 4*71. The experimental density of colo¬ 
phene given in Gmelin’s Handbook exceeds what would 
be required by Coolly. No member of the second group, 
however, had been examined in this respect, unless it be 
cedrene, which appears to belong to it, and which gave, 
according to Walter, the vapour density 7*5. C 15 H 24 re¬ 
quires 7*06. I took the oils of patchouli and calamus. 
* Phil. Trans. 1863, p. 317. . 
fi Since writing the above, I find the same conclusion had 
been previously arrived at by Oeser. 
