[chadsky] decomposition OF POTASSIUM CHLORATE 23 



Thus from Table 1 we find : — 



Weight of oxygen from KCIO^ KCl = 0.0022 gr. 

 Weight of oxygen required for KCIO^ = 0.0003 gr. 

 Loss of weight (oxygen evolved) =^ 0.0017 gr. 



We may conclude, therefore, that at least under ordinary conditions 

 the formation of perchlorate takes place only during the simultaneous 

 evolution of free oxygen. 



The majority of the experiments were carried out at temperatures 

 separated by ten or twenty degrees, beginning at 400°. At each tem- 

 perature, with a few exceptions, three tests were made, lasting respec- 

 tively, one, two and three hours, for the purpose of ascertaining the rate 

 at which the reaction proceeds. The results of these experiments are 

 expressed by the numbers in Table 1, and by the curve diagrams. In 

 these the total quantity of chlorate heated is given the value 100, so that 

 the weights of chlorate changed to perchlorate and chloride, as well as 

 the weight remaining unchanged are expressed directly as percentages. 

 It is to be observed that the weight of chloride or of perchlorate is not 

 given, but the weight of chlorate that has changed to chloride or per- 

 chlorate. The oxygen is expressed in percentages of the total oxygen in 

 the chlorate. 



The numbers in Table 1 show that the reactions take place more 

 slowly as they proceed. In other words the reactions appear to be re- 

 tarded by the presence of the resulting substances. Politzin (Loc. cit.), 

 in his investigations upon barium and calcium chlorates found that the 

 reactions in the case of these salts, as indicated by the amount of 

 chloride formed, are at first somewhat accelerated and then retarded. 

 Whether there is any original acceleration with potassium chlorate 

 can scarcely be shown by the method I have used, owing to the fact 

 that for short periods, the time required to attain the final tempera- 

 ture, viz., three or four minutes, is a larger fraction of the total time 

 than for longer periods. Original acceleration is, however, a matter 

 of very great frequency in chemical reactions, and it probably occurs 

 in this case. Subsequent retardation might, indeed, be expected, owing 

 to two circumstances. In the first place the increasiing amount of 

 chloride, mixed with the chlorate results in the " dilution " of thf^ 

 reacting substance, and in the second place, the perchlorate forme(? 

 decomposes more slowly than the chlorate at the same temperature. 



It is also evident that in the majority of cases the amount of 



chlorate changed to perchlorate is larger than the amount changed to 



chloride. This may be expressed by saying that the fraction 



KCIO., — KCJO^ 



r— - — is usually greater than unity. It may reach the 



