4ife M, Balard on a peculiar Substance [Dec. 



scarcely becoming black by exposure to light, and is thus distin- 

 guished from bromuret of silver, which is yellow, curdy, and 

 readily altered by the solar rays. Bromate of potash does not 

 precipitate the salts of lead, whereas the hydrobromate of potash 

 occasions a very abundant crystalline precipitate in them ; with 

 protonitrate of mercury the bromate of potash forms a yellowish 

 white precipitate which is soluble in nitric acid. Bromate of 

 potash possesses a property of which the chlorates are destitute, 

 but which exists lo a great extent in the iodates ; its acid is 

 decomposed by the influence of hydrogenating causes, as if it 

 were uncombined ; thus sulphurous acid, sulphuretted hydrogen, 

 hydrobromic acid and muriatic acid, react upon the bromate of 

 potash, and produce in the three first cases a disengagement of 

 brome, and in the last instance a compound of brome and 

 chlorine. 



I tried, but in vain, to obtain an oxide of brome by the decora- 

 position of bromate of potash ; it is true indeed that the failure 

 may be owing to the small quantity of the substances upon 

 which I am able to make my researches. 



Hydrobromic acid, when diluted with water, evolves brome by 

 agitation with bromate of potash. Diluted sulphuric acid pro- 

 duces at 212° Fahr. a disengagement of gas, which I attempted 

 to collect over water, mercury, and oil. I always procured 

 brome and oxygen gas, which seems to show, either that brome 

 cannot form oxides, or that the compounds, if they could 

 be procured, are less permanent than the oxides of chlorine. 



Bromate of potash may be obtained by a different process 

 from that which I have described. It is sufficient to combine 

 brome and chlorine, and to mix potash with the aqueous solution 

 of the compound, and instantly there is produced the decompo- 

 sition of water, a bromate and muriate of potash ; these salts, on 

 account of their different solubility, are easily separated. I 

 employed this process for the preparation of bromate of barytes, 

 which I obtained in the form of acicular crystals, soluble in 

 boiling water, slightly soluble in cold water, and burning with a 

 green flame upon red-hot charcoal. 



When dilute sulphuric acid is poured into an aqueous solution, 

 of bromate of barytes so as to precipitate all the base, the 

 remaining solution is one of bromic acid, from which the greater 

 part of tho water may be separated by slow evaporation ; it then 

 acquires the consistence of a syrup : if the heat be raised so as 

 completely to expel the water, a portion of the acid is vaporized, 

 and another portion is decomposed into oxygen and brome ; 

 similar effects appear to be produced by evaporating the fluid in 

 vacuo with sulphuric acid ; water, therefore, appears to be requi- 

 site to the constitution of bromic acid. 



Bromic acid reddens tournsol paper strongly, and soon after 

 decolorizes it j it has scarcely any smell, its taste is very acid, 



