196 



REPORT — 1871. 



the purity of the aqueous solution, that the acid be previously lique- 

 fied, and its vapoiir pasfsed slowly into water, as has been recommended 

 by Brandeau. As the cold weather had all vanished before I could secure 

 time to enter on this investigation, I saw it was hopeless to prepare the 

 liquid acid readily and thus ensure a pure product, but made a few observa- 

 tions on the purest product I could obtain — the highest number I have 

 obtained per equivalent of chlorous acid, ClO^, acting on hydriodic acid 

 amounting to 111,000 units, the following reaction taking place, thus, 



C103-f-4HI=HCH-3H0 + I,. 



It is easy to calculate the heat absorbed during the formation of dilute 

 chlorous acid, and it is found to amount to —27,800 heat units. 



Similar observations have been made on peroxide of chlorine obtained 

 from the action of oxalic acid on chlorate of potash. The aqueous solution 

 of the gas has always contained appreciable quantities of free chlorine, and 

 the value obtained will necessarily require some correction. One equivalent 

 of ClOj acting on hydriodic acid evolves 120,000 heat units ; the following 

 reaction takes place : — 



C10,-1-5HI=HC1 + 4H0+L. 



When the requisite numbers are inserted in the above equation, the result 

 is found to be 19,800 heat units absorbed for the formation of an equivalent 

 of peroxide of chlorine. 



The thermal values of chlorous acid and of peroxide of chlorine are likely 

 to require considerable correction, because I have not found that strict uni- 

 formity in the results I should have liked. This is owing in great part to the 

 difficulty of procuring a pure product, and the great tendency to secondary 

 decomposition. The mode of conducting the experiments may also have con- 

 siderable influence on the results. The above experiments wei'c made with 

 the relative proportions of the oxides of chlorine and of hydriodic acid that 

 would completely neutralize each other, so as to precipitate the iodine in the 

 free state. A sei'ies of experiments made in presence of excess of hydriodic 

 acid, the requisite correction being made for the solution of the iodine, 

 would be important, and these I intend to execute along with farther ob- 

 servations on this subject. 



The following observations have been made in connexion with this re- 

 port : — 



Action of dilute HCl on dilute HCIO, nothing 



I 



10. 



KHO 



I 



HI 



HI 



CIO3 



CIO, 



HCIO3 nothing 



H,0 — 730 



10, 15,000 



HCIO^ 36,500 



HCIO3 nothing 



HIO- (per eq. of HI). . . . 10,000 



HI (per cq. of CIO3) 111,000 



HI (per eq. of ClOJ .... 120,000 



