1886.] 



Conduction and Molecular Composition, fyc. 



287 



mean to contend that the metals are fully neutralised in their 

 compounds, but merely that as a rule they behave as though they were 

 saturated just as do the C ;i H 2w _ 7 radicles derived from the benzenes. 

 There can be little doubt that an absolute distinction must be drawn 

 between hydrogen and the metals on the one hand, and the non- 

 metals on the other. Regarding the facts in the light of our 

 knowledge of carbon compounds, it is difficult to resist the conclusion 

 that the differences observed are due to differences in structure of the 

 stuffs of which the elements as we know them are composed, the 

 which differences condition perhaps a different distribution of the 

 electric charge or its equivalent, in the case of each element. 



In the earlier part of this paper I have ascribed the influence which 

 the one set of molecules of the composite electrolyte exercise upon the 

 other during electrolysis to the existence of "residual affinity." I 

 believe this view also to apply to the explanation of the occurrence of 

 chemical change. To quote the words of Arrhenius, " L'activite 

 electrolytique se confonde avec l'activite chimique." Several pregnant 

 examples of this have already been given by Ostwald (" J. pr. Chem.," 

 1884, 30, p. 93). 



The investigation of the nature of chemical change has assumed an 

 altogether different aspect since the publication of Mr. H. B. Dixon's 

 inquiry into the conditions of chemical change in gases ("Phil Trans.," 

 1884, p. 617 ; see also " Chem. Soc. Trans.," 1886, p. 94). Mr. Dixon 

 has clearly proved that it is impossible to explode a mixture of carbonic 

 oxide and oxygen, and that the change 2CO + 2 = 2C0 2 is effected 

 when sparks are passed across the tube containing the gaseous mixture 

 only in the path cf the discharge. If traces of water be present explo- 

 sion takes place, the velocity of propagation of the explosive wave 

 increasing with the amount of water up to a certain maximum. 

 These results completely dispose of the popular explanation of such 

 changes, viz., that the molecules in the path of the discharge undergo 

 dissociation, that the dissimilar atoms thus liberated then combine 

 together, and that as the heat developed in their union causes the 

 dissociation of yet other molecules, change gradually extends through- 

 out the mass.* Mr. Dixon's experiments have not only shown that 

 the propagation of change is dependent on the presence of a third 

 body, but that this third body must bear a certain relation to those 

 with which it is associated ; C0 2 , CS 2 , C 2 N" 2 , CC1 4 , S0 2 , and rT 2 were 

 found by him to have no action, and only water — or bodies which 

 formed water under the conditions of the experiment — were found 

 capable of determining the explosion. There is an obvious difference 



* I am not to be understood to imply that dissociation does not take place in the 

 path of the discharge ; on the contrary, for all the facts appear to me to indicate 

 that conduction and electrolysis are inseparable phenomena in gases as in liquids." 

 (Comp. Schuster, " Proc. Koy. Soc," 1884, p. 317.) 



