178 Scientific Intelligence. 



similar in appearance to those of nitrous acid, and at 116.5° F. it enters in- 

 to ebullition. It retains its liquid form at the temperature of zero of Fah- 

 renheit's thermometer. 



• Brome is a non-conductor of electricity, and undergoes no chemical 

 change from the agency of the imponderables. It was transmitted through 

 a red-hot glass tube, and exposed to the action of a voltaic pile, sufficiently 

 powerful for disuniting the elements of water, without evincing the least 

 trace of decomposition. It supports combustion in a very feeble manner :— 

 alighted taper immersed in the vapour of brome is soon extinguished ; 

 but before going out, it burns a few seconds with a flame which is green at 

 its base and red at its upper part, as in an atmosphere of chlorine. 



Brome is soluble in water, in alcohol, and particularly in ether. It does 

 not redden litmus paper, but bleaches it rapidly like chlorine ; and it like- 

 wise discharges the blue colour from a solution of indigo. 



From these points of close resemblance between brome and chlorine, M. 

 Balard was led to examine its relations with hydrogen. No chemical ac- 

 tion takes place between the vapour of brome and hydrogen gas at com- 

 mon temperatures, not even by the agency of the direct solar rays ; but on 

 introducing a lighted candle or a piece of red-hot iron into the mixture, 

 combination ensues in the vicinity of the heated body, though without ex- 

 tending to the whole mixture, and without explosion. The union is rea- 

 dily effected by the action of brome on some of the gaseous compounds of 

 hydrogen. Thus on mixing the vapour of brome with hydriodic acid, sul- 

 phuretted hydrogen, or phosphuretted hydrogen gases, decomposition fol- 

 lows, and a colourless gas, possessed of acid properties, is generated. The 

 hydro-bromic acid gas may be conveniently procured for experimental pur- 

 poses by a process similar to that for forming hydriodic acid. A mixture 

 of brome and phosphorus, slightly moistened, yields a large quantity of 

 pure hydro-bromic acid gas, which may be collected over mercury. 



The hydro-bromic acid gas is colourless, has an acid taste, and a pun- 

 gent odour. It irritates the glottis powerfully, so as to excite cough, and 

 when mixed with moist air, yields white vapours, which are denser than 

 those occasioned under the same circumstances by muriatic acid gas. It 

 undergoes no decomposition when transmitted through a red-hot tube, 

 either alone, or mixed with oxygen. It is not affected by iodine; but 

 chlorine decomposes it instantly, with production of muriatic acid gas, 

 and deposition of brome. It may be preserved without change over mer- 

 cury ; but potassium and tin decompose it with facility, the first at com- 

 mon temperatures, and the last by the aid of heat. 



The hydro-bromic acid is very soluble in water. The aqueous solution, 

 may be made by treating brome with sulphuretted hydrogen dissolved in 

 water, or still better, by transmitting a current of hydro-bromic acid gas 

 through pure water. The liquid becomes hot during the condensation, 

 acquires a great density, increases in volume, and emits white fumes when 

 exposed to the air. This acid solution is colourless when pure, but pos- 

 sesses the property of dissolving a large quantity of brome, and then re- 

 ceives the tint of that substance. 



