Chemistry, 1 79 



Chlorine decomposes the solution of hydro-bromic acid in an instant. 

 Nitric acid likewise acts upon it, though less suddenly, occasioning the 

 disengagement of brome, and probably the formation of water and nitrous 

 acid. The nitro-hydro-bromic acid is analogous to aqua regia, and pos- 

 sesses the property of dissolving gold. 



The elements of sulphuric and hydro-bromic acids react on each other in 

 a slight degree ; and hence on decomposing the hydro-bromate of potassa 

 by sulphuric acid, the hydro-bromic is generally mixed with a little sul- 

 phurous acid gas. 



The metallic oxides, as might be expected, do not act in an uniform 

 manner on the hydrc-bromic acid. The alkalies, earths, the oxides of 

 iron, and the peroxides of copper and mercury, form compounds which 

 may be regarded as hydro-bromates ; whereas the oxide of silver, and the 

 protoxide of lead, give rise to double decomposition, in consequence of 

 which water and a metallic bromuret result. 



The composition of hydro-bromic acid gas is easily inferred from the two 

 following facts. 1. On decomposing hydro-bromic acid by potassium, a quan- 

 tity of hydrogen remains precisely equal to half the volume of the gas em- 

 ployed ; and 2. when hydriodic acid gas is decomposed by brome, the re- 

 sulting hydro-bromic acid occupies the very same space as the gas which is 

 decomposed. It is hence apparent that the hydro-bromic is analogous to 

 hydriodic and muriatic acid gases ; or, in other words, that 100 measures 

 of hydro-bromic acid gas contains fifty measures of the vapour of brome, 

 and fifty of hydrogen. 



Since brome decomposes the hydriodic, and chlorine the hydro-bromic 

 acid, it is obvious that brome, in relation to hydrogen, is intermediate be- 

 tween chlorine and iodine, its affinity for that substance being weaker than 

 the first, and stronger than the second. The affinity of brome and oxygen 

 for hydrogen appears nearly similar, for while oxygen cannot detach hy- 

 drogen from brome, brome does not decompose watery vapour. 



The action of brome on the metals presents the closest resemblance to 

 that which chlorine exerts on the same substances. Antimony and tin 

 take fire by contact with brome ; and its union with potassium is attended 

 with such intense disengagement of heat as to cause a vivid flash of light, 

 and to burst the vessel in which the experiment is performed. M. Balard 

 is of opinion, that the soluble metallic bromurets are converted, like the 

 similar compounds of chlorine and iodine, into neutral hydro-bromates, 

 and reciprocally, that the hydro-bromates are frequently converted into 

 bromurets in passing into the solid state. All the bromurets are decomposed 

 by chlorine with evolution of brome ; and the hydro-bromates are not only 

 attacked by chlorine, but by all substances, such as the chloric or nitric 

 acids, which have a strong tendency to deprive other bodies of hydrogen. 



The bromuret of potassium, which may be obtained in cubic crystals 

 from the hydro-bromate of potassa by evaporation, was found by M. Balard 

 to consist of 



Brome - - 65.56 



Potassium - - 34.44 



