222 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS; [September 21 , 1872. 
and if the lieat is raised to about 132° C. (270° F.), 
the colour will not deepen. At a somewhat higher 
temperature, particularly when nearing 150° C. 
(302° F.), the liquid soon becomes darker and finally 
black. 
When the temperature has reached 132° C.— 
which should require not less than three hours— 
the fire is withdrawn and the retort allowed to cool 
to about 50° or 55° C. (120° to 130° F.); the contents 
are dissolved in 12 oz. of petroleum benzine, and 
the solution is poured into a beaker glass containing 
some warm water and pieces of marble to neutralize 
the free acid still present. While cooling, the ben¬ 
zine solution is occasionally stirred to disturb the 
crystallization. On the following morning, the 
liquid matter is poured off, the benzine mother- 
liquor separated from the aqueous solution of bro¬ 
mide of calcium, and the crystals drained upon a 
funnel, the neck of which is loosely stopped with 
some cotton. Petroleum naphtha or gasoline is 
poured upon them until they change but little in 
colour when exposed to the direct sunlight. When 
dry the crystals will weigh about twelve ounces; for 
complete purification they require to be recrystal¬ 
lized from alcohol or petroleum benzine. 
More crystals may be obtained by evaporating 
the benzine mother-liquor to one-lialf and washing 
them first with the naphtha solution and then with 
some fresh naphtha. The mother-liquor, not yield¬ 
ing sufficiently pure crystals, is evaporated, heated 
in a retort to 260° C. (500° F.), when it boils again, 
evolving liydrobromic acid. When the evolution of 
the latter slackens, the black mass, after cooling 
sufficiently, is taken up with benzine, the solution 
treated, as before, with warm water and an alkali 
(marble) and set aside to crystallize; the black 
crystals are redissolved in alcohol or benzine, the 
solution filtered and crystallized. The crystals 
require to be washed with petroleum naphtha, and 
on recrystallization are obtained pure. The re¬ 
maining mother-liquors which on concentration do 
not yield any crystals, are evaporated, and the 
oily matter reserved for a subsequent operation. 
Monobromated camphor crystallizes from alcohol 
in thin white or colourless prisms or needles; 
from petroleum benzine, it may be obtained in 
long, fiat prisms, which are perfectly transparent 
and hard, and assume the appearance of shining 
scales when crystallizing rapidly from a very con¬ 
centrated solution. It is entirely insoluble in water, 
but readily and freely soluble in alcohol, ether, and 
in less than its own weight of hot petroleum ben¬ 
zine, from which solution the greater portion crys¬ 
tallizes on cooling. It is permanent in the air 
and is not affected by the direct sunlight. Boiled 
with water it evaporates very slowly, condensing 
in the neck of the retort in fine white interlaced 
needles. Its odour is somewhat camplioraceous, 
not very strong, but persistent, and reminding of 
Borneo camphor; the taste likewise reminds of 
camphor, and is terebinthinate and scarcely bitter. 
It fuses at about 67° C. (170° F.), and boils with 
partial decomposition at 274° C. (525° F.) Accord¬ 
ing to Swarts, it forms with hydrochloric and 
liydrobromic acids, oily compounds, crystallizing 
after having been warmed for some time, in soft 
scales. This is very j>robably the oil-like matter 
remaining in the first mother-liquor, and requiring 
for its decomposition a temperature of 260° C. 
(500° F.) But even then the decomposition is not 
complete, and Perkin found that the product ob¬ 
tained by his process at 274° C., required to be freed 
from oil by pressing between bibulous paper. Long 
continued application of heat (200° C.), and treat¬ 
ment with potassa may perhaps effect it. Its de¬ 
composition by the action of light and air may 
probably be expressed thus: C 20 H 15 BrO 2 , FIBr= 
2 Br-f C 20 H 16 O 2 . 
When boiled with a solution of nitrate of silver 
in nitric acid, monobromated camphor is decomposed 
and bromide of silver precipitated. From this he 
amount of bromine was calculated, and the follow¬ 
ing results obtained:— 
20 C 
THEORY. 
120 
51.95 
I. 
FOUND. 
II. Ill, 
15 H 
15 
6.49 
— 
- - 
Br 
80 
34.63 
34.59 
34.57 34.64 
2 O 
10 
6.93 
— 
— — 
No. I. 
231 100.00 
was monobromated camphor crystallized 
from petroleum benzine; II., crystallized from alco¬ 
hol, and, III., obtained by heating the oily compou 
of the first mother-liquor to 260° C. and crystalliz n d 
from petroleum benzine. 
ON A METHOD OF DETERMINING THE EXPLOSIVE 
POWER OF GASEOUS COMBINATIONS. 
BY JAMES DEWAR. 
In a paper recently read before the Royal Society of 
Edinburgh, the author describes an apparatus by means 
of which the explosive power of gaseous combinations 
can easily be determined, and from this, by Bunsen’s pro¬ 
cess, the temperature may readily be calculated. The 
essential feature of the apparatus is the registration of 
the “ compression volume ” of a given initial volume of 
air, on which the gaseous explosive mixture has been 
allowed to act. As the duration of the pressure is all 
but instantaneous, the well-known formula 
P 2 /VA 1-4 
W = W 
may be employed to ascertain the final pressure, more 
especially as the sudden rebound prevents any great loss 
of heat. In order to test the apparatus many experiments 
were made with mixtures of hydrogen and oxygen, and 
the mean result arrived at was a condensation to one- 
fifth the original volume of air (the initial volume being 
measured at 30 in. bar), when pure electrolytic gas was 
employed. This is equivalent to a pressure of 9 "5 atmo¬ 
spheres, and therefore agrees with Bunsen’s previous 
determination. The author hopes to be able to execute 
a series of determinations under varying conditions of 
temperature and pressure. 
ORGANIC CHEMISTRY AND THERAPEUTICS. * 
BY A. W. HOFMANN. 
(Continued from p. 206f 
Not only has the direct employment of glycerine re¬ 
sulted in advantage to therapeutics, but also the investi¬ 
gation of its metamorphoses, a study which has been 
followed with great zeal by chemists. It has long been 
known that the remarkable irritant properties of pow- 
* Lecture delivered at the Medical Chirurgical Institute of 
I Berlin. 
