68 SCIENCE PROGRESS 



which the rate of diminution in volume of the electrolytic gas 

 ought to have increased gradually and steadily from zero to a 

 constant value. A second objection raised was that on repeating 

 Bevan's experiments on the formation of clouds in the rapidly 

 expanded gases, we failed to discover any facts which could not 

 be readily explained without invoking the aid of a new class of 

 condensation nuclei. Moreover Dyson and Harden {Trans. 

 Cheui. Soc. 1903, 83, 29) had pointed out that the theory of an 

 intermediate compound could not be reconciled with the 

 " induction period " observed by them with an almost dry mix- 

 ture of chlorine and carbon monoxide. It was evident that the 

 hypothesis in question would have to be abandoned and that the 

 true cause of the " period of chemical induction " had not as yet 

 been disclosed. A systematic study of the conditions controlling 

 the manifestation of the inert period was therefore undertaken 

 in the hope of elucidating the cause of the phenomenon. It 

 was soon discovered that the source of the initial inertness of 

 the mixture resided as much in the liquid used in the actinometer 

 to absorb the hydrogen chloride as in the gas itself; moreover, 

 that the property of imparting inertness to the gas was possessed 

 in very different degrees by different liquids. Experiments on 

 the following lines had forced this conclusion upon us. 



An actinometer, filled in the usual way with electrolytic 

 gas, was exposed to light until the maximum rate of inter- 

 action had been reached ; the duration of the induction period 

 was duly recorded. The actinometer was then shaken so 

 as to bring the liquid into intimate contact with the gas and 

 again exposed to light ; another inert period of shorter dura- 

 tion than the first was observed. On again shaking the 

 actinometer and then re-exposing it to light, a third induction 

 period shorter still than the second became manifest. By the 

 constant repetition of these operations the contents of the 

 actinometer were at length brought into such a condition that 

 no further indication of an induction period was noticeable on 

 shaking. The results show clearly enough that the cause of 

 the inertness resides in the liquid and can be communicated 

 to the gas and that it is destroyed on exposure of the 

 latter to light. A series of experiments was next performed 

 in which the absorbing liquids were aqueous solutions of 

 salts and mineral acids. In these circumstances, the induction 

 periods observed were often many times longer than when 



