December 23,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
513 
UromWnp of Sritntifit Sonelies. 
CHEMICAL SOCIETY. 
At the Meeting of this Society, on Thursday, Decem¬ 
ber 7th, Professor Frankland, F.R.S., in the chair, Dr. 
J. H. Gladstone, F.R.S., read a paper on “ Essential 
Oils,” in continuation of one read before the Society eight 
years since. As we may have an opportunity of printing 
this paper in full on a future occasion, at present we only 
give a brief abstract. The first group of oils described 
included citrin, lign aloe, pimento, and oil of villvert. 
The hydrocarbons from essential oils were divided into 
three polymeric groups, having the formula} C 10 H 16 , 
C 13 H 24 , and C 20 H 32 , and the line of demarcation observed 
in oomparing their physical properties pointed out. 
Many of the essential oils are mixtures of a hydro¬ 
carbon with a compound containing oxygen, of which 
but few have hitherto been carefully examined. Those 
obtained from citronella and from wormwood the author 
calls citronellole and absinthole respectively: they both 
have the composition C 10 H lf) O, the most remarkable 
point of difference between them being in their refrac¬ 
tion equivalents; that of absinthole being 74*5, which 
agrees closely with the theoretical for C l0 H 16 O, while 
citronellole has 79-3 or 79-8 for its equivalent, a dis¬ 
crepancy almost the same as that found throughout the 
great phenyl group. Besides these he has examined 
cajeputole from oil of cajeput, and also the two carvoles 
from oil of caraway and oil of dill. These appear to be 
identical and not merely isomeric, and are remarkable 
for forming a crystalline compound with sulphuretted 
hydrogen having the composition (C 10 H 14 O) 2 H 2 S. The 
physical properties of menthole from spearmint, myris- 
ticole from nutmeg, and hydride of cumanyl from cassia, 
have likewise been examined; the latter has the enor¬ 
mous refraction of 1-6045 for the line A, and its refrac¬ 
tion equivalent is also very abnormal. 
In the discussion that followed, the President said 
that the paper which Dr. Gladstone had communicated 
to the Society was one of great importance, since these 
physical qualities were facts which would remain un¬ 
alterable however much our views as to the theory of 
their constitution might change, and although no one 
admired this class of investigation more than he did, he 
might also be allowed to speak a word in favour of cer¬ 
tain chemical reactions which might, perhaps, enable us 
to relegate these hydrocarbons to their proper families, 
such as the action of chlorine or bromine on them. He 
should like to elicit from the author if he had tried any 
such reaction, so as to distinguish, for example, whether 
they were hydrides or radicals. 
Dr. Gladstone said that bromine and chlorine deriva¬ 
tives had been prepared, but that the result had been 
unsatisfactory. 
Dr. AVright asked whether his researches had led the 
author to consider the hydrocarbons as isomeric in the 
same way that the butylic hydrides are, or was it pos¬ 
sible that many of these hydrocarbons might be identical, 
the difference in their properties being due to accidental 
impurities. 
Dr. Gladstone replied that these oils were distin¬ 
guished in some cases chiefly by their optical properties, 
and in others by their odour: citronellole was distin¬ 
guished from absinthole by the former having a con¬ 
siderably higher refractive equivalent than the theo¬ 
retical, like that found in compounds throughout the 
great phenyl group ; and again, the carvol from dill and 
the carvol from caraway were considered to be identical 
and not isomeric, from having the same odour; the same 
might be said of the eugenic acid from pimento and from 
cloves; identity of odour alone, however, is not suffi¬ 
cient to establish the identity of the hydrocarbons. 
Dr. Wright suggested that the odour might be due to 
a chemical change which the substance undergoes in the 
presence of oxygen, and in contact with the mucous 
membrane of the nose. It was well known that hydro¬ 
carbons which had been recently distilled over sodium 
had a less powerful odour than they had after being 
exposed for some time to the air. 
Professor A. H. Church referred to the very interest¬ 
ing sulphur compound (C ]0 H 14 O) 2 H 2 S, in which an 
oxidized oil was united with sulphuretted hydrogen. 
Some eight or nine years ago he had described tasmanite, 
a resin found in a shale from Tasmania, which contained 
oxygen and sulphur in the same relative proportions as 
the above-mentioned compound. This resin, when 
treated with sulphuric acid, evolved sulphuretted hy¬ 
drogen, so that the sulphur was in oi^anic union with 
it, and not like the sulphur found in coal. In another 
fossil resin, dysodile, which he had examined, the sulphur 
and oxygen only approximated to that ratio, but then it 
was not pure. 
Dr. II. E. Armstrong then read a paper entitled 
u Observations on Nitrochlorophenols.” 
SOCIETY OF ARTS. 
Dyes and Dye-Stuffs other than Aniline.* 
BY DR. CRACE-CALVERT, F.R.S. 
Lecture III. 
Blue Colouring Substances. — Indigo , Orchil , Cudbear , 
Litmus , Prussian Blue and Ultramarine. 
{Continued from page 496.) 
The carmines of indigo are especially used by silk- 
dyers, in consequence of the removal of the green co¬ 
louring matter above referred to, and which, if allowed 
to remain, would spoil the blue or purple which they 
wish to obtain. The method practically adopted to as¬ 
certain if the sample has been well washed, consists in 
rubbing a small quantity of it on a piece of glazed 
paper, which, when the colour dries, gives a colour vary¬ 
ing from a pale blue to a rich copper purple, according 
to the mode of manufacture; and if any green colouring 
matter is left in, it shows itself as a green ring round 
the blue circle. 
The following may be taken as the composition of a 
sample of carmine of indigo of fair quality :—• 
Water . « ..85 
Indigo.10'2 
Saline residue ...... 4-8 
100-0 
The sulpho-indigotic acids are especially, used by 
woollen-dyers, who add to the dye-beck a little alum 
and cream of tartar, which helps the fixing of the indigo 
on the wool. The green colouring matter is in this case 
not objectionable, having no affinity for the fibre of 
wool. _ 
The carmines of indigo, as well as the sulpho-acids, 
are easily decolorized by reducing agents, such as hy¬ 
drogen and sulphuretted hydrogen, but they gradually 
reassume their original colour when exposed to the 
atmosphere, through the absorption of oxygen. 
The above compounds, not being suitable for dyeing 
cotton, and not giving colours on silk and wool that may 
be considered fast, I shall now proceed to describe a few 
of the methods followed to obtain fast indigo blues. 
They are all based on the principle of the reduction of 
blue indigo into white indigo. The latter compound is 
held in solution by an alkali, which enables the dyei oi 
printer to introduce it into the fibre oi the fabric, whei e, 
on exposure to the atmosphere, the alkali combines w ith 
carbonic acid, and the white indigo thus liberated absoibs 
* Cantor Lecture, delivered Tuesday, Feb. 21. Reprinted 
from the Journal of the Society of Arts. 
