Section III., 1903 [ IS ] Trans. R S. C. 



II. — The Rate of Decomposition of Potassium Chlorate under the 

 Influence of Heat. 



By S. B. Chadsey. 



(Communicated by Dr. W. H. Ellis, and read May 20th, 1903.) 



The experiments outlined in the following paper were carried out 

 with the object of obtaining a knowledge of the course of the changes 

 which potassium chlorate undergoes when subjected to the action of heat. 

 It was recently shown by Sodeau (J. Chem. Soc, 1900, p. 138), that 

 pure potassium chlorate when heated yields only very small quantities 

 of chlorine, so that the changes consist almost entirely in the formation 

 of potassium perchlorate, potassium chloride and oxygen. The rate of 

 the decomposition of the chlorates of calcium and barium was studied 

 by Potilitzin in 1887. (J. Euss. Chem. Soc, 1887; Ber., 1887; Eef. 

 769). But as I have met with no reference to similar determinations 

 for potassium chlorate it seemed desirable to carry out a series of experi- 

 ments in which quantities of chlorate could be heated at various con- 

 stant temperatures and the products of the decomposition measured. 



The chlorate used in the experiments was prepared from the com- 

 mercial "pure" salt by repeated recrystallization, and was shown to be 

 perfectly neutral and free from chlorides. Special precautions were 

 taken to prevent contamination with dust, and lint from filter paper was 

 avoided by allowing the chlorate obtained from the last recrystallization 

 to drain on unbaked porcelain. The purified product was dried at 110°, 

 pulverized and again heated at 110° for three hours to ensure the re- 

 moval of all moisture. Subsequent ahsorption of small quantities of 

 moisture was avoided by keeping the dried salt in a desiccator. 



Amounts of 0-5 gm. enclosed in bulbs blown on tubes of soda glass, 

 20-25 cm. in length and 7 mm. in diameter, were heated in a small elec- 

 tric dental furnace (Dr. C. A. Timme, Berlin), of internal dimensions 

 8 cm. X 8 cm. x 4-3 cm. The tubes containing the chlorate were placed 

 horizontally in the furnace through a small opening in the fire-clay 

 door, and by this arrangement splashes of the molten chlorate were re- 

 tained by the upper surface of the bulb, and were not carried into the 

 cool parts of the tube. 



The furnace was heated by means of the 110 volt public circuit, 

 regulated roughly by a large coil rheostat, and more closely by a lamp 

 rheostat in parallel with the latter (Fig. 1). But as the large varia- 

 tions in the voltage of this circuit prevented the maintenance of con- 

 stant temperatures a supplementary circuit of storage cells was arranged 



