5(j THE r.EHAVIOUR OF SOLUTION'S OF HVDRIODIC ACID 



At the end (if tAveiitv-four lunirs on openinji- the >top-{'ock again, 

 a lariie qnantity of oxygen was fonnd to huUhle through the 

 ?ohiti(in, shdwiiig that some of the oxygen thi-re had heen nsed 

 np dnring tlie twentv-fonr hours. Kverv dav as uuieh oxygen 

 as possible was forced into the hotth^s containing the solution, 

 until at the end of al)out nine weeks, the solution had lost all 

 its cnldiir, with the cxccjition of the slight })ecnliar colour men- 

 tioned ])reviously. Some of the solution was drawn off and 

 tested for iodine and iodides, but not the least trace of either 

 was fonnd to be present. The passage of oxygen into the solu- 

 tion was continued with the result, that at the end of another 

 week, the slight colour possessed by the solution entirely dis- 

 ap[>eared. During this time it was roughly estimated that not 

 less than twenty-iive litres of oxygen, at the ordinary tempera- 

 ture of the laboratory and a pressure somewhat above the 

 normal, were passed into the iodide solution. 



On the foregoing grounds then, it is not unreasonable to 

 suppose that the iodine is being transformed into some oxygen 

 compoun<l, ;ind that this transforniation is accelerated by light. 



Creighton and Mackenzie^ have shown in the case of solu- 

 tions of hydriodic acid acted upon by radium, M'here the iodine 

 content after a time begins to diminish, it is very probable it is 

 the hydriodic acid that is transformed and not the iodine itself, 

 thus lessening the content of free iodine by upsetting the equili- 

 brium between the two substances. On account of the similar- 

 ity between the two cases, it is possible that this is the manner 

 i)i which the cha.ige takes ])hic(' here. 



The colourless solutions from which the iodine had dis- 

 appeared were now examined. It was found tiiat these solu- 

 tions containc;] no iodide, but,, however, a small (]uantity of 

 iodate. If these sohifinii^ wei'c allowed to stand foi- a few weeks 

 after becoming cohmrless, before testing, there could not be 

 obtained the sliiditest trace of iodate. These facts would seem 



1 Lor. cit. 



