POTASSIUM CHLORATE. 407 



When melted and heated too suddenly, it is decomposed with 

 incandescence, and sometimes causes dangerous explosions. 



2. The equivalent of potassium chlorate is 122*6. 



3. Composition 



Oxygen 392 



Potassium 319 \ 



Chlorine 289 / 



608 



1000 



4. Density, 2'33. 



5. Heat of formation 



Cl + O 3 + K = C10 3 K liberates + 94 Cal. 



6. The salt melts at 334, without undergoing decomposition, 

 at least if the operation is carried on at constant temperature. 

 It decomposes slowly at 352, but more rapidly if the tempe- 

 rature be suddenly raised. 



This decomposition is effected by two distinct processes. 

 The salt heated with precaution yields a large quantity of 

 potassium perchlorate 



4C10 3 K = KC1 + 3C10 4 K, 



a reaction which liberates + 51*5 Cal., but which would give 

 rise to no gas if it were developed alone. 



As a matter of fact, it is always accompanied by another 

 transformation, effected on a considerable portion of matter, 

 viz. the direct decomposition of potassium chlorate into potassium 

 chloride and oxygen 



C10 3 K = KC1 + 3 . 



The latter reaction becomes more and more predominant, 

 according as the operation takes place at a higher temperature, 

 or as the substances are superheated. It even seems to be the 

 only one that takes place in presence of copper oxide or of 

 manganese dioxide. 



7. This decomposition, referred to the ordinary temperature, 

 liberates +11 Cal. at constant pressure, or + 11*8 at constant 

 volume. 



This makes per kilogramme, 81 '6 Cal. at constant pressure 

 and 8 7 '4 Cal. at constant volume. 



At 350 and upwards, this reaction liberates more heat, the 

 potassium chlorate being melted, but the exact figure cannot be 

 given, the melting heat of the salt not having been measured. 



8. We thus obtain 33'48 litres of gas (reduced volume), or, 

 per kilogramme, 2731 litres at the normal pressure and at 0. 



9. The molecular specific heat of potassium chloride being 

 12*9 and the special molecular heat of oxygen, O 3 , at constant 

 volume, 7'4, this makes in all 20 -3. From this we conclude 



