REACTIONS OF HALOGENS AND ALKALIS. 363 



(+ 22*6), acids diverge still more, one from the other, and 

 present differences which are not the same as for their salts. 



9. Let us now compare the three principal reactions to which 

 the systems formed by halogens and alkali are susceptible. 



(?) 



3C1 2 gas + 3K 2 (diluted) = 3KC10 (dissolved) + 3KC1 (dissolved) + 76-2 



KC10 3 (dissolved) + 5KC1 (dissolved) + 94-2 



6KC1 (dissolved) + 3 +111-0 



The liberation of heat and the stability continue to increase 

 from the hypochlorite to the chlorate and free oxygen. 



w 



3Br 2 (gas) + 3K 2 (dissolved) = 3KBrO (dissolved) + 3KBr (dissolved) + 57-6 



KBr0 3 (dissolved) + 5KBr (dissolved) + 54'0 



6KBr (dissolved) + 3 + 74'4 



The formation of hyprobromite liberates a rather greater 

 quantity of heat than that of the bromate, which explains the 

 relative stability of the former compound. However, the forma- 

 tion of bromide and oxygen is still the reaction which liberates 

 most heat. It is, moreover, well known that concentrated 

 potash can yield oxygen by its action on free bromine. 



" w 



3I 2 + 3K 2 = 3KIO (dissolved) + 3KI (dissolved) ... + 24-9 - 3a 



KI0 3 (dissolved) + 5KI (dissolved) l + 31-8 



6K1 (dissolved) + 3 ' - 12'3 



Here the formation of the iodate exceeds all the others. The 

 liberation of oxygen would even involve an absorption of heat, 

 contrary to what takes place with the chlorate and bromate. 

 Moreover, this liberation does not take place at the ordinary 

 temperature ; it is only effected with the aid of a foreign energy 

 which is got in the act of heating. 



We see that the principal chemical circumstances attending 

 the formation of the combinations between oxygen and the 

 halogens are in harmony with thermal data. 



1 Calculated from the figures on p. 360, admitting that they represent a 

 maximum value for the formation of hypoiodite. 



