II. Chemistry notes

Abstract

The first step towards the direct formation of this and other chloro-bromides is, of course, the preparation of the solution of chloride of bromine. This I endeavoured to prepare by a process analogous to that by which I had formed the chloride of iodine. I found, however, that in passing the chlorine into the bromine and water, a larger quantity of the former is carried off in the form of vapour. I continued the passage of the gas, nevertheless, till all the bromine was dissolved and the solution assumed a faint yellow tint. On conducting olefiant gas into this, I obtained a very small quantity of an oily liquid, part of which boiled between 106° and 110° Cent. Altogether, it is by no means a productive progress. I made an ineffectual effort to improve it by surrounding the vessel containing the bromine with ice.This, however, only made matters worse, as it caused the formation of solid hydrate of chlorine and of bromine, which prevented the completion of the process. After several unsuccessful experiments I at last hit upon the following process, which answers remarkably well:—500 grains of bromine are dissolved in 4 fluid ounces of a mixture of equal volumes of strong hypochloric acid and water. This solution is introduced into a flask with a long neck, and surrounded with ice. Washed chlorine is then passed into it with repeated agitation, till it ceases to be absorbed. In this way not a trace of bromine is lost, nor are any solid hydrates formed during the passage of the gas. On conducting olefiant gas into this solution, which should be surrounded with cold water and repeatedly agitated, I obtained a large quantity of an oily liquid, which I separated from the acid solution, washed with dilute potash, and distilled. Almost the entire quantity passed over between 106° and 110°, most between 108° and 110°. The following analysis proves that this was the body in question in a state of purity:— C 2 H 4 ClBr. Theory. Experiment. Carbon. . . . . . 16.72 16.57 Hydrogen . . . . 2.78 3.01 This process yields nearly 80 per cent. of the theoretical quantity. Chloro-bromide of propylene (C 3 H 5 ClBr).