DECOMPOSITION OF HYDRIODIC ACID. CREIGHTON. 9 



In the third and fifth columns of Table II. are added num- 

 bers calculated from the equation 



2/ = a (1-e-") 

 with the values of a and h there given, to show how well the 

 observations are represented by curves of this type. These 

 calculated curves are plotted in tigure (1), the amounts of 

 sodium thiosulphate solution being represented as abscissae. 

 The observed values are marked and lie remarkably well on the 

 curves. The similarity of these two curves seems to show that 

 with pure water, at this temperature, the action of radium is of 

 the same nature as that which goes on without it in the dark, 

 but is greater. 



