102 Proceedings of the Royal Irish Academy. 



why they should be specially affected at the temperatuie at %vhich water 

 boils under normal pressure. The results obtained by Lauster' are of 

 interest in this connexion. Lauster investigated the effect of temperatuie 

 by removing the ions in an air-stream previously heated. He determined 

 the mobilities in close proximity to the flame. Under these circumstances 

 the mobility of the ions without any special heating varied from about -1 to 

 about '02, the value found increasing with the rapidity of the air-stream. When 

 the temperature is increased the mobility remains constant up to a certain 

 point, and then a rapid increase sets in. The critical temperature is about 

 45" C. for the ion of mobility 'I, and seems to increase to about 50" C. for 

 the ion of mobility circa "2. Lauster regards the rapid increase of mobility 

 at the critical temperature as indicating the disintegration of the ionic 

 complex. As the critical temperature increases with the size of the ion it is 

 possible that the temperatures determined by him correspond to our value 

 100° C. for the large ion. 



A number of experiments were carried out in which the gas from the 

 flame was conveyed to the measuring vessel without being allowed to cool. 

 The following values for the mobilities were obtained : — 

 Temperature. Mobility. 



50" C. -00088 



80° C. .0040 



]20°C. -0082 



165° C. -018 



All those values are higher than those found at similar temperatures 

 by the other method. It is clear that in this case the ions have not 

 attained a stable condition. The equilibrium sizes peculiar to each tempera- 

 ture are probably closer to the values given by the graphs of fig. 3 than they 

 are to the values found with the uncooled gas. 



Experiments on the effect of temperature have also been carried out by 

 Dr. H. Kennedy with a different apparatus. His results on the effects of 

 heating up ions which had been allowed to grow to their stable condition, 

 while not so complete as those given above, are in general agreement. 

 From a great number of observations carried out by him at difierent tem- 

 peratures when the ions came directly from the flame it would appear that 

 the size of the ions depends not so much on the temperature as on the time, 

 size of the flame, and other conditions. Generally there was present a 

 mixture of ions of two classes. The mobilities were higher than those found 

 by us. 



' Lauster, loc. cit. 



