DECOMPOSITION OF HYDRIODIC ACID. CRE1GHTON. 17 



TABLE VI. 



If these numbers are plotted it is seen that the curves are 

 straight lines below 16C. If the latter are produced backward 

 they will cut the axis of temperature at about 12C. and 

 3C. for the radium and no radium curves respectively. At 

 these temperatures there should be no decomposition unless the 

 curves should become asymptotic, and, considering the steepness 

 of the curves at 0C., this would not seem probable for the "no 

 radium " curve at least. Of course it was out of the question 

 to keep the solution at 12C. on account of its freezing, but 

 a solution could easily be kept at 3G. for a time. 



This temperature ( 3C.) was easily obtained by placing the 

 solution in a bath of very dilute alcohol, which was surrounded 

 by a mixture of salt and snow. It required but little attention 

 to keep this bath at a temperature of about 3 6C. to 4C. 



It was found at the end of ten hours that the decomposition 

 in a solution not under the influence of radium, and kept at a 

 temperature of 3C. during that time, was equivalent to 

 0.19 cc. sodium thiosulphate. Hence the curves at 0C. must 

 cease to be straight lines, and begin to run asymptotically 

 toward the axis of temperature. 



PROC. & TRANS. N. S. INST. Sci., VOL. XII. TRANS. 2. 



