NITRIC PEROXIDE AND BARIUM DIOXIDE. 169 



A volume of the alkaline solution containing a weight of chlorine 

 precisely equal to that of the nitric peroxide was then taken, 

 and the bulb containing the acid placed in it. The bulb was 

 then opened by the breakage of one of its points, taking care 

 that the mixture of the two solutions should be gradual, and the 

 heat liberated during the reaction measured. 



Lastly, an excess of dilute hydrochloric acid is added to the 

 solution, the heat liberated by this addition being also measured. 

 Thus the whole is brought to a very simple final state, that of a 

 weak aqueous solution, formed by an equivalent of potash, an 

 equivalent of nitric acid, and a known proportion of hydro- 

 chloric acid somewhat greater than an equivalent. 



In an independent experiment the heat liberated by the 

 mixture of the three components taken directly in the same 

 proportions and degree of dilution as in the above experiment 

 was measured. 



This being known it is easy to deduce from the data obtained 

 the heat liberated by the following transformation : 

 N0 2 gas + Cl gas + H 2 -f water = HN0 3 dilute + HC1 dilute. 



The weight of N0 2 being 2-281 grms 17-9 Cal. 



1-125 grms 17'7 



Mean 17-8 



deducting from this value the difference in the heats of forma- 

 tion of dilute hydrochloric acid, viz. : 



39-3 - 34-5 = + 4-8, 



we find, 2N0 2 liquid + gas + water = 2HN0 3 dilute + 13*0. 

 Adding now the heat of vaporisation of nitric peroxide, we obtain 

 2N0 2 + gas + water = 2HN0 3 dilute + IT'3. 1 



The heat liberated by the transformation of nitric oxide and 

 oxgyen into dilute nitric acid, + 35*9 Cal., being taken as 

 known, we shall definitely have for the heat liberated by the 

 formation of gaseous nitric peroxide, from its immediate com- 

 ponents, 2NO + 2 = 2N0 2 gas -f'35'9 - 17'3 = 18'6 according 

 to the experiments of the second process. 



4. Third Process. Nitric peroxide and barium dioxide. This 

 process is based on the following reactions, 2N0 2 -J- Ba0 2 

 = (N0 3 ) 2 Ba. But this reaction does not take place with pure 

 and anhydrous bodies under the conditions adapted for calori- 

 metric measurements, and the following method was used. 



The liquid nitric peroxide is weighed in a bulb, then the 



1 Thomson obtained for this reaction the value + 16-9. In order to 

 measure it, he adopted the following process, which is less certain than that 

 indicated in the test. He allowed the nitric peroxide gas to act upon water, 

 so as to dissolve it, which liberates + 7-75 ; then he introduced chlorine into 

 the liquor, which liberates + 14-28 more, and he derives from these data the 

 heat of oxidation of nitric peroxide gas, forming dilute nitric acid. 



