170 OXYGENATED COMPOUNDS OF NITKOGEN. 



equivalent barium dioxide is weighed, the latter is dissolved in 

 dilute hydrochloric acid and the heat liberated measured. Next, 

 nitric peroxide is allowed to react gradually upon the solution 

 which escapes from one of the broken points of the bulb which 

 is completely immersed in the solution. The heat liberated 

 during this second reaction is also measured. 



The sum of the two results gives the total heat corresponding 

 to the following transformation 



2N0 2 liquid -f Ba0 2 anhydrous + 2HC1 dissolved = 2HN0 3 

 dissolved + BaCl 2 dissolved. 



It is immaterial whether we suppose the baryta united with 

 the hydrochloric acid, or with the nitric acid, or shared between 

 both, since the heat liberated by the union of this base with 

 either acid is the same. 



The foregoing experiment was made with pure and anhydrous 

 barium dioxide. 



The heat of formation from anhydrous baryta and free oxygen 



BaO + = Ba0 2 liberates + 6'05 Cal. 1 



This quantity being known, as well as the heat of solution of 

 anhydrous baryta in dilute hydrochloric acid (+ 27*8) ; lastly, 

 the heat liberated by the reaction of nitric acid (formed from 

 nitric peroxide) upon dilute barium chloride being sensibly nil ; 

 the calculation of the experiments made with nitric peroxide 

 enables the heat liberated in the following reaction to be 

 arrived at 



2N0 2 liquid + gas + H 2 = 2HN0 3 dilute. 

 Thus 



Weight. Found. 



N0 2 2-279 + 12-4Cal. 



N0 2 1-358 +12-2 



N0 2 0-951 +12-6 



Mean + 12'4 



In order to pass to gaseous N0 2 we must add the heat of 

 vaporisation of this body, viz. -f 4*33 ; which makes altogether 

 + 16-73. 



Finally, this number deducted from the heat of formation of 

 dilute nitric acid by nitric oxide and oxygen (viz. + 3 5 '9) 

 gives for the formation of nitric peroxide gas from nitric oxide 

 and oxygen, + 35'9 - 16*73 = + 19-17. 



5. To sum up, the reaction NO + = N0 2 gas liberates 



According to direct experiment + 19'4 



the reaction of nitric peroxide gas on chlorine ... + 18-57 

 the reaction of nitric peroxide on barium dioxide +19-17 



Mean + 19-04 



1 " Annales de Chimie et de Physique," 5 e se"rie, torn. vi. p. 209. 



