66 Prof. W. M. Thornton on the Nature of Chemical 



thermal agitation at ordinary temperatures appears to be 

 necessary to enable the electron to effect a permanent union 

 with an uncharged molecule of the gas or impurity. 



3. For the vapour of petroleum ether, whose molecules 

 contain only atoms of carbon and hydrogen, the negative 

 carriers appear to consist practically entirely of free 

 electrons ; a trace of impurity, however, is sufficient to effect 

 the production of a considerable number of negative ions. 



4. A brief investigation has been made of the motion of 

 free electrons through C0 2 ; the results do not indicate that 

 the velocity of the electron is proportional to the applied 

 field, but suggest that the electron may traverse a consi- 

 derable distance with accelerated motion before its terminal 

 velocity is acquired. 



5. In no instance was any evidence obtained of a change 

 in the nature of either the positive or the negative ion as the 

 pressure of the gas was reduced. 



6. The present method was employed to determine the 

 values of the ionic mobilities for a few vapours; the results 

 have been compared with previous determinations. 



7. A discussion is given with regard to the bearing of the 

 results on certain outstanding problems of ionic theory. 



The University of Sydney, 

 December, 1916. 



IV. The Nature of Chemical Affinity in the Combustion of 

 Organic Compounds. ByW. M. Thornton, D.Sc, D.Eng., 

 Armstrong College, Newcastle-upon-Tyne* . 



1. rilHE final stage in the combustion of organic com- 

 JL pounds is combination in a gaseous state. Affinity 

 is then probably of the simplest kind, for molecules are far 

 apart, and they are in contact for the briefest possible time. 



In the absence of any knowledge of how an electron, 

 acting as a bond, is anchored into the atomic structures of 

 combining atoms, the force that a bond sustains may be 

 assumed as a first approximation to obey the usual laws of 

 attraction and to be proportional to the products of the 

 nuclear charges — that, is of the masses of the molecules. It 

 is clear, however, that affinity is not a simple electrostatic 

 attraction, and that between elements it is dependent upon 

 atomic formation. 



2. The most recent comparisons of affinity in gases are 

 those of Prof. W. A. Bone and colleagues f made by ex- 



* Communicated by the Author. 



t " Gaseous Combustion at High Pressures," by Prof. W. A. Bone 

 and others, Phil. Trans. Roy. Soc. ser. A, vol. ccxv. pp. 275-318. 



