174 OXYGENATED COMPOUNDS OF NITROGEN. 



Dilute hydrochloric acid is at once added in considerable 

 excess, which liberates a fresh quantity of heat, Q x . Under these 

 conditions the whole of the chlorine introduced at the outset, 

 is at the end, and in a moment, changed into hydrochloric acid, 

 as can be easily proved. The final as well as the initial state 

 is therefore completely definite. The sum 



Q + q + Qi 



represents the total heat liberated during the passage from the 

 initial to the final state ; or, for C1 2 = 71 grms. 



* x 71 = S. 



P 



The heat liberated, from the initial to the final system, is 

 therefore 69 + S. 



But we could have passed from the same initial to the same 

 final state according to the following succession unite 2H with 

 2C1, forming 2HC1 dilute, liberating + 78-6 Cal. ; then unite 

 nHCl dilute with nBaO dissolved, forming nBaC! 2 dissolved, 

 which liberates + 13'85n ; lastly unite 2 gaseous -f Ba (N0 2 ) 2 

 dissolved, which produces Ba(N0 3 ) 2 dissolved, liberating x. The 

 thermal sum being the same in both processes, we have the 

 equation 



S - 13-85n - (78-6 - 69) = x. 



Three concordant experiments, made according to this process, 

 each on about 2 grms. of nitrite, yielded 



x = 221 Cal., 



a value which corresponds to the following reaction, Ba(N0 2 ) 2 

 dissolved -f- 2 gas = Ba(N0 3 ) 2 dissolved. The precautions em- 

 ployed in these experiments to avoid the use of gaseous chlorine, 

 either in a neutral or acid medium, and also against the sudden 

 transformation of the chlorine into chloride, or the variable form- 

 ation of oxides of chlorine, should be observed; 1 free hypochlorous 

 acid has also been included, because this acid is difficult to 

 obtain quite free from chlorine or the higher oxides of chlorine, 

 besides, it decomposes spontaneously, and also in presence of 

 bodies which it oxidises, especially in an acid medium. 2 



Second process. Barium dioxide. The barium nitrite is 

 changed into nitrate by barium dioxide dissolved in hydrochloric 

 acid. Ba(N0 2 ) 2 dilute + 2BaO 2 + 4HC1 dilute = Ba(N0 3 ) 2 

 dilute + 2BaCl 2 dilute + 2H 2 0. 



The initial system is the following : 



Ba(K0 2 ) 2 dilute, 2BaO anhydrous ; 2 gas ; 4HC1 dilute, 

 all these bodies being separate. 



The final system is the following : 



Ba(N0 3 ) 2 dilute, 2BaCl 2 dilute + 2H 2 0. 



1 " Annales de Chimie et de Physique," 5 e serie, torn. v. p. 322. 



2 Ibid., p. 342. 



