6C1 + 3H 2 + water = 3HC10 (diluted) + 3HC1 (diluted) liberates 



SUCCESSIVE DEGREES OF OXIDATION. 349 



sensibly the same. When hypochlorite is changed into 

 chlorate 



3KC10 (dissolved) = KC10 3 (dissolved) + 2KC1, 

 heat is liberated to the amount of 



-f 18'0, for potassium salts ; 4- 18'3, for sodium salts ; + 19'9, 

 for barium salts. 



The second decomposition, that of the dissolved chlorate into 

 chloride, liberates -f- 16*8 for the three salts as before stated. 



The conversion of dissolved chlorate into perchlorate liberates 

 sensibly the same quantity of heat. 



It is seen that the relative stability of the solutions keeps 

 increasing from the hypochlorite to the chlorate, then to the 

 perchlorate and to free oxygen, which is consistent with what 

 we know from chemistry. 



Finally, if we refer the actions to the formation of the acids 

 themselves, which gives at least the heat liberated by their 

 union with the bases, we have 



+ 5-7 



_____ + 12-0 

 liberates +28-9 

 28-8 



The thermal relations, therefore, remain the same. 



11. Successive degrees of oxidation. Let us now examine the 

 heats of formation of the different acids of chlorine. 



From the experiments performed 



A2 + C1 2 + 2 + water = H 2 0, C1 2 2 (dilute)] absorbs ... - 2'9 

 H 2 + C1 2 + 5 + water = H 2 0, C1 2 6 (dilute)] absorbs - 12-0 



H 2 + C1 2 + 7 + water = H 2 0, C1 2 7 (dilute)] liberates + 4-9 



There is then, in the first place, an absorption of heat which 

 increases according as the proportion of oxygen united to equal 

 weights of chlorine increases in the compound ; this is the case 

 for the first two compounds. 



But, on the contrary, heat is liberated in the case of the 

 third, to the extent of -f- 16*9 for ; formation of perchloric 

 acid. 



The same relations subsist if we take oxygen as the unit and 

 vary the chlorine. For a given weight of oxygen, such as 

 [0 5 ] = 40 grms., united to 01 = 35 '5 grms. in dissolved 

 chloric acid, there is an absorption of 12'0. The same weight 

 of oxygen, when united to C1 6 = 177*5 in dissolved hypo- 

 chlorous acid, gives rise to an absorption of 



-2-9x5=- 14-5, 



which is more considerable. But this increase in the heat 

 absorbed does not extend to perchloric acid ; it, on the contrary, 



