284 Mr Connell on the Relation of 



was made abundantly manifest by the same reagents. A like 

 result was obtained, when an ucid was employed which had been 

 highly charged with nitrous acid, by passing through it a cur- 

 rent of deutoxide of azote. 



From these experiments, it seems to follow that, under the 

 influence of bromine and nitrous acid, a portion of water is de- 

 composed by long continued boiling, hydrobromic acid, and 

 probably nitric acid, being formed. This result is somewhat re- 

 markable, because, under ordinary circumstances, nitric and 

 hydrobromic acids mutually decompose one another. It does 

 not appear that all the bromine employed becomes hydrobromic 

 acid, a part of it being usually volatilized. 



As it would appear that the precautions necessary for dimi- 

 nishing the loss of iodine in the preparation of iodic acid by the 

 action of nitric acid have not been well understood *, I think it 

 proper to add the following particulars, willingly leaving to 

 others the determination of the comparative merits of the diflPer- 

 ent methods which have been proposed for the preparation of 

 iodic acid. 



The essence of the method by nitric acid, consists in using a 

 vessel of very large capacity in relation to the quantity of mate- 

 rials employed. I would recommend that it should be capable 

 of containing forty or fifty times the quantity of nitric acid ac- 

 tually used. The reasons obviously are, to afford a large in- 

 ternal surface on which the iodine volatilized may be condensed, 

 and from which it may be washed back again into the acid, and 

 to diminish the quantity of acid-vapour escaping by the neck, 

 which ought to be as narrow as possible "f. A very strong acid 

 ought also to be employed, and the boiling is best maintained 

 by the small flame of a spirit-lamp, so as to prevent, as much as 

 possible, the heating of the sides of the vessel. Operating in this 

 way, although I have always experienced some loss of iodine, yet 

 I do not conceive that, with due care, the loss is so great as to 



• See Annales de Chimie et de Physique, xlix. 144; andAnnaL der Phys. 

 xxiv. 363. 



-f- It is very convenient in washing back the iodine, to be able occasion- 

 ally to fit in a glass stopper, so that the liquid may reach etery part of the 

 vessel, without danger of being spilt. 



