HYPERCHLORIC ACID. 371 



perchloric and oxichloric acid, is obtained from chlorate of 

 potash in different ways. At that particular point of the decom- 

 position of chlorate of potash by heat, when the evolution of 

 oxygen is about to become very violent, the fused salt is in a 

 pasty state, and contains, as was first observed by Serullas, a 

 considerable quantity of hyperchlorate, the oxygen extricated 

 from .one portion of chlorate being retained by another portion 

 of the same salt. This salt is rubbed to powder, and dissolved 

 in boiling water, from which the hyperchlorate is first deposited, 

 on cooling, owing to its sparing solubility. The same salt may 

 also be prepared by throwing chlorate of potash in fine powder 

 and well dried, into oil of vitriol gently heated in an open bason, 

 by a few grains at a time, when the liberated chloric acid re- 

 solves itself into chlorous acid and hyperchloric acid, the former 

 coming off as a yellow gas ; thus : 



RESOLUTION OF CHLORIC ACID INTO CHLOROUS ACID AND 

 HYPERCHLORIC ACID. 



Before decomposition,. After decomposition. 



{2 Chlorine _^^ 2 Chlorous acid. 

 8 Oxygen 

 7 Oxygen 

 Chlorine """ -*Hyperchloric acid. 



Of the 3 equivalents of potash, previously in combination 

 with the chloric acid, one remains with hyperchloric acid as 

 hyperchlorate of potash, and the other two are converted into 

 bisulphate of potash. The whole reaction between the acid and 

 salt may, therefore, be thus expressed : 



3KO, C1O 5 and 4HO, SO 3 = 2C1O 4 and KO, C1O 7 

 and 2(HO,SO 3 + KO, SO 3 ) and 2HO. 



In conducting this operation, the greatest caution is neces- 

 sary, owing to the explosive property of chlorous acid ; for if 

 the order of mixing the substances be reversed, and the acid 

 poured upon the chlorate, or if too much chlorate be added at 

 a time to the acid, a most violent and dangerous detonation 

 may occur. But this reaction is chiefly interesting as affording 

 chlorous acid ; for hyperchlorate of potash may be obtained from 

 chlorate by the action of nitric acid, lately observed by Professor 

 Penny, without danger or inconvenience. The chlorate is tran- 

 quilly decomposed in nitric acid gently heated upon it, the chlo- 



B B 2 



