and o/'Iodme oii Vegetable Colours. 839 



I have made several attempts to effect the acidification of 

 bromine by a process similar to that which succeeded in regard 

 to iodine. I poured a few drops of bromine into a glass-tube, 

 about eight inches long, and closed at the lower extremity, and 

 then added a little nitric acid. The liquid was heated in some 

 experiments to ebullition, and in others to a temperature short 

 of that point, the upper end of the tube being kept cooled by 

 moistened bibulous paper, and the mouth loosely stopped. The 

 bromine, as it rose in vapour, was condensed in the upper part 

 of the tube and fell back in drops into the acid, and as the pro- 

 cess went on, the tube was occasionally inclined, to absorb the 

 vapour which filled it. This process was continued till little 

 bromine appeared either in the liquid or in the state of vapour. 

 The fluid was then poured out into an evaporating basin, and 

 concentrated by heat, but I could get no evidence of the exist* 

 ence of bromic acid in it *. 



The fact, that iodine may be acidified by the agency of ni- 

 tric acid, independently of affording a ready method of pro- 

 curing iodic acid, seems not without interest, as illustrating the 

 nature of iodine. Many substances of the class of simple in- 

 flammable bodies, both metallic and non-metallic, may, as is 

 well known, be acidified by means of nitric acid. Iodine, like 

 chlorine and bromine, was long thought to have so little affinity 

 for oxygen as to be incapable of directly uniting with it. But 

 the recent experiments of Sementini f have rendered it extreme- 

 ly probable that iodine may be oxidated by simple contact with 

 oxygen at a high temperature ; and the fact, that at the tempe* 

 rature of ebullition iodine takes oxygen from nitric acid, and 

 becomes iodic acid, appears to point out another link of connec- 

 tion, in addition to the many already known, between iodine 

 and the class of simple combustible substances, although, of 



• Since this paper was written, I have repeated the experiment of boil- 

 ing together nitric acid and bromine in a longer tube, the upper extremity 

 of which was bent and terminated in water, with the view of condensing any 

 volatile products; the adjoining portion of the tube being kept cool as before. 

 The aqueous liquid was then gently heated till all the free bromine which 

 had passed over appeared to be expelled. Even then it was largely precipi- 

 tated by nitrate of silver, but the precipitate, from all its properties, appeared 

 to be merely bromide of silver ; and I have not yet had time to ascertain why 

 the precipitate was so abundant. 



•f- See Journal of Roval Institution for August 1831. 



y2 



