422 Mr. W. H. Pendlebury and Miss M. Seward. 



cannot be taken. At temperatures above 35 the starch-iodide colour 

 is very difficult to perceive, as it loses its distinctive blue tinge and 

 acquires a purple colour. At temperatures below 0, though the 

 starch colour is then a most beautiful blue, yet the change proceeds 

 so slowly that it becomes difficult to hit, even within a few minutes, 

 the point at which the blue colour has definitely appeared. Hence 

 the range of temperature is somewhat limited. 



This brings our work to a conclusion. There are several points 

 which still need elucidation ; their interpretation has seemed, so far, 

 beyond our powers. We can only add a few facts to the pile now 

 rapidly accumulating, out of which should grow a comprehensive 

 theory of chemical dynamics. 



The facts established by the investigation may be thus summa- 

 rised : 



Dilute solutions of hydrogen chlorate and hydrogen chloride when 

 mixed together slowly liberate oxidising material, chlorine and 

 oxides of chlorine. 



If no substance which can be oxidised is present, the accumula- 

 tion of this oxidising material in the liquid soon stops the reaction. 



In the presence of an iodide from which iodine can be liberated, 

 and afterwards disposed of by means of sodium thiosulphate. the re- 

 action proceeds regularly and with a constant velocity constant 

 because the quantity of the substances decomposed bears an infinitely 

 small relation to the quantity present. 



The actual rate varies with the quantity of hydrogen chlorate, in 

 the first place directly as it is the substance decomposed, and in the 

 second place with a small acceleration proportional to the quantity, 

 the substance thus having a coefficient of acceleration independent of 

 its being that undergoing decomposition. Thus 



where R is rate of decomposition, Q quantity. The variation with 

 quantity of hydrogen chloride is not of so simple a nature. This acid 

 would seem to have (1) an effect of the secondary order above men- 

 tioned (accelerative) on the decomposition of hydrogen chlorate 

 alone ; and in addition to this (2) an effect of both primary and 

 secondary order as above on the decomposition of hydrogen chlorate 

 by hydrogen chloride. 



The addition of potassium chloride to the liquid has a small accele- 

 rative effect on the rate proportional to its quantity. 



If a mixture of solution of potassium chlorate and hydrogen 

 chloride is made (in molecular proportion between 1 : 2 and 1 : 12), 

 complete double decomposition ensues. The hydrogen chlorate formed 

 in presence of the remaining hydrogen chloride liberates oxidising 



