or THE DESTEUCTIVE DISTILLATION OF BOGHEAD COAL. 
739 
the mercury rapidly rising until 123° is reached, after which the rise becomes very slow. 
When the propyle and benzole have distilled away, and the point of ebullition of the 
fluid is elevated to 150° or upwards, rapid evolution of hydrobromic acid takes place, 
accompanied by a vapour acting powerfully on the eyes. The distillate at this point 
acquires a flne blue colour. It being plain from these phenomena that the hyperhalyde 
produced by the action of bromine could not be prepared in a state fit for analysis, the 
residue in the retort was mixed with a strong alcoholic solution of potash, in order to 
obtain a halyde capable of being distilled without decomposition. On mixing the two 
fluids there was a great rise of temperature, and a large quantity of bromide of potas- 
sium crystallized out. Sometimes the bromine compound and the alcoholic potash were 
cohobated together, at others the halyde was prepared by mere digestion of the ingre- 
dients and subsequent precipitation of the oil by water ; even cohobation over solid 
hydrate of potash produced the same result. The brominated oil thus prepared was 
colourless, very dense, and had a powerful odour, somewhat resembling iodide of amyle. 
Although the hyperhalyde was prepared from a fraction of almost constant boiling-point, 
and purified carefully by distillation on the oil-bath, all coming over below 130° being 
rejected, yet the halyde produced from it was not homogeneous, its boihng-point varying 
from 80° to 150°. 
MM. Beethelot and De Luca have shown in their memoir on iodized propylene the 
great difficulty of obtaining pure products of this class, owing to the simultaneous 
formation of other substances, both fixed and volatile ; and it is evident that if such a 
difficulty is found with that substance, it must exist to a much greater extent with a 
homologue having so comparatively high an atomic weight as that yielding the com- 
pound under consideration. In order to lessen the sources of error, the bromine com- 
pound w'as fractionated previous to analysis, but, despite every precaution, numerous and 
perfectly concordant analyses showed the impossibility of obtaining it free from oxygen. 
This arose from the mode of preparation. The formula of the brominated oil was, origin- 
ally, C’^ H" Br, but oxidation had proceeded so far as to make the composition almost 
agree with the expression C'^H’'BrO. The cause of the oxidation of the monobromi- 
nated caproylene or hexylene will become apparent from the following experiments. 
It has been said that when the hydrocarbons were treated with bromine in presence 
of water, the fluid separated after a time into three layers, the upper being water con- 
taining a small quantity of hydrobromic acid, the middle the brominated oil, and a lower 
stratum. The latter, on separation by a tap-funnel, proved to be highly acid and per- 
fectly soluble in w'ater. It distilled, with very little evolution of acid fumes, at 127°. 
A piece of paper moistened with it and held near the fire, became jet-black at the spot 
touched. Excess of precipitated carbonate of lime was added, and, as soon as effer- 
vescence had ceased, the whole was boiled for a few minutes and filtered. The solution 
evaporated to dryness yielded a white and highly deliquescent mass, a qualitative ana- 
lysis of which indicated the presence of bromine and calcium. A portion was heated to 
redness, rapidly cooled in a platinum crucible with a well-fitting lid, and the per- 
centage of calcium estimated. 
5 D 2 
