.[chadsey] decomposition OF POTASSIUM CHLORATE 19 



Results for one détermination are given in the following: 



Weight of chlorate heated — 0-5 gms. Temperature 500°. 



1. Weight of KCIO^ changed to KCl = 0.1566 gr. 



2. Weight of KCIO^ unchanged = 0.0738 gr. 



3. Weight of KCIO^ changed to KCIO, = 0.2646 gr. 



4. Weight of oxygen set free in (1) = 0.0613 gr. 



5. Oxygen required for KCIO^ = 0.0345 gr. 



6. Loss of weight of bulb = 0.0260 gr. 



Now the sum of (5) and (6) should equal (4) 



0.0345 — 0.0260 = 0.0605 

 0.0613 — 0.0605 = 0.0008 



In this connection is to be mentioned the continual increase in the 

 weight of the bulbs used in these determinations which amounted in 

 some cases to as much as 5 milligrams for one heating. It seems prob- 

 able that these two phenomena are to be attributed to the same cause. 

 Sodeau in his work with barium chlorate, J. Chem. Soc, 1900, p. 138, 

 found that at atmospheric pressure, practically no chlorine reached the 

 potassium iodide bulbs, through which the gases from the chlorate were 

 passed, but that at pressures reduced to a few mm., considerable quanti- 

 ties of iodide were decomposed, while the alkalinity of the residue was 

 very slightly different in the two cases. This seems to indicate that 

 heated glass may absorb small quantities of chlorine. It is unlikely, 

 however, that the total increase in the weight of the bulbs is due to 

 chlorine, for an increase of 0.0020 gms. would indicate that 1-4^ of the 

 total chlorine had been evolved and the results of Sodeau show that this 

 ■quantity is much too large. It is possible that a certain quantity of 

 K^O reacts with the glass to form soluble manganates, so that it seems 

 very likely that a large part of the increase of weight is due to the ab- 

 sorption of oxygen. 



General reasons for this may be made apparent by an examination 

 of the method of analysis and the results obtained. The reaction under 

 consideration may be qualitatively represented thus : 



KCIO, = KCl + KCIO^ + K.^0 + C^ + 



Now in the analysis the KCl is first estimated. It is evident that 

 the greater the amounts of KM and CI, the less the amount of KCl, 

 and consequently the smaller will be the calculated amount of oxygen 

 liberated. By lessening the true amount of KCl, the amount of KCIO^ 

 is increased, since this is obtained by difference and consequently the 

 amount of oxygen required for KCIO^ is made greater. Thus we have 

 the weight which is found to be greater, — namely the weight of oxygen 

 evolved, less than its true amount, while one of the parts of the sum 



