.1826.] On a peculiar Substance contained in Sea Water, 411 



Article IV. 



Memoir on a peculiar Substance contained in Sea Water, By 

 M. Balard, Apothecary and Chemist to the Faculty of Sci- 

 ences, at Montpelier. 



{Concluded from p. 3S7.) 



Certain metals act upon liquid hydrobromic acid; iron, 

 zinc, and tin, are dissolved by it with the evolution of hydrogen.; 

 metallic oxides when put into this acid act differently upon it, 

 the greater part of them, the alkalies, the earths, the oxides of 

 iron, and the peroxide of copper and mercury, form fluid combi- 

 nations which may be regarded as hydrobromates ; there are 

 some oxides with which the hydrobromic acid undergoes double 

 decomposition, and produces water and metallic hydrobromu- 

 rets ; such are the protoxide of lead and the oxide of silver. 

 ' Those oxides which contain much oxygen, and have no 

 affinity for hydrobromic acid, or which cannot, by decomposing 

 it, form corresponding bromurets at this high degree of oxida- 

 tion, lose a certain quantity of their oxygen, which determines 

 the decomposition of apart of the hydrobromic acid, and conse- 

 quently there is a. disengagement of brome. The less oxygenated 

 oxide afterwards forms with the acid which escapes decomposi- 

 tion an hydrobromate, or a metalUc bromuret. It is an action of 

 this kind which is exerted by the peroxides of lead, antimony^ 

 and manganese. The last compound may be employed with 

 hydrobromic acid to prepare brome ; this method, which resem- 

 bles that for the preparation of chlorine gas, is easier than that 

 which I have previously described. 



It will be observed that brome has less affinity for hydrogen 

 than chlorine has, but it is greater than that of iodine ; hydrogen 

 combines readily with chlorine, but it is more difficult to unite it 

 directly with iodine and brome. Chlorine decomposes water at a 

 high temperature; brome and iodine do notdecompose it under 

 similar circumstances. Hydrobromic acid is decomposed by 

 chlorine, but brome in its turn also decomposes hydriodic acid. 

 The action of metals upon these hydracids leads to the same 

 consequences. The hydriodic acid is decomposed by the action 

 of mercury ; pure hydrobromic acid may, on the contrary, be 

 long kept on this metal without undergoing any sensible altera- 

 tion ; but at a moderate temperature, it begins to be decona- 

 posed by tin, which would have exerted no action upon muriatic 

 acid. 



It results from this unequal affinity, that the properties of 

 hydrobromic acid are in some degree intermediate between thosB 

 of muriatic and hydriodic acids. If it resemble the first by the 

 difficulty with which it is decomposed, by the united influence 



