IN LIGHT IN THE PRESENCE OF OXYGEN. CREIGHTON. 59 



Pt + 2KC1. From this the amount of potassium was deter- 

 mined. It was found that: 



(1) 0.4890 gram of residue yielded 0.9674 gram Pt + 2KC1. 



(2) 0.4890 " " 0.9610 " 



mean 0.9642 " " 



This corresponds to 0.2193 gram of potassium, which is 44.83 

 per cent, of the residue used. 



These results are arranged in the following wav so as to be 

 more obvious : 



Theoretical composition Composition of residue examined, 

 of K 2 S0 4 (1) High results. (2) Low results. 



Potassium 44.87% 44.98% 44.68% 



Sulphuric acid(SO;). 55.13% 54.81% 54.73% 



100.00% 9979% 99.41% 



When the weights of the substances corresponding to these 

 percentages are calculated for 1.4914 grams there is obtained: 



Theoretical Residue examined, 



for K.,S0 4 (1) High results. (2) Low results. 



Potassium 0.6694 g. 0.6699 g. 0.6664 g. 



Sulphuric acid (SOp 0.8220 g. 0.8175 g. 0.8162 g. 



1.4914 g. 1.4874 g. 1.4826 g. 



It will be seen that 1.4914 grams of the residue used, cor- 

 respond to 14.81 cc. of solution, and should therefore contain 

 0.0100 gram iodine. The above analysis shows the difference 

 between this amount of residue and the amounts of potassium 

 and sulphuric acid (SO 1 ^) that it contains. The discrepancy 

 between this difference and the amount of iodine that should 

 be in the residue can'not be accounted for at present. 



Although the results of this investigation have been nega- 

 tive in the main, nevertheless some information as to the 

 behaviour of hydriodic acid in the presence of oxygen and 



