ON ELECTROLYSIS. 339 



the molecules of an electrolyte going on always before any E.M.F. has 

 been applied. 



Professor Fitzgerald now points out that without some further hypo- 

 thesis it is not legitimate to assume that, because the least E.M.F. produces 

 an electrolytic current, therefore there can be no force keeping the atoms 

 in the molecules, and that consequently they must be in a continual state 

 of interchange. If the work done during the combinations be equal to 

 that required for separating the atoms in the molecules, then the least 

 E.M.F. may produce its corresponding current. The Williamson-Clansius 

 hypothesis is that these are both zero ; but this is by no means the only 

 possible hypothesis. In order that it shall be the only possible hypothesis 

 it must be further assumed that the energy for decomposing a molecule 

 cannot be transferred without considerable loss from a combining mole- 

 cule. Any orderly connection amongst the molecules set up by the 

 electric polarisation that would enable a transference of energy to take 

 place from the combining to the decomposing molecules would explain 

 the fact that the least E.M.F. produces its corresponding current ; but if 

 no such orderly relations amongst the molecules are possible then the 

 Williamson-Clausius hypothesis seems to be almost certainly established. 



This refers, of course, only to the reasons founded on electrolysis for 

 the Williamson-Clausius hypothesis. The chemical reasons founded on 

 the phenomena of double decomposition are independent evidence in its 

 favour, except that there seems some diflBculty in seeing how gases cap- 

 able of double decomposition are not decomposed by the feeblest E.M.F. 



Concerning the mode in which electrolytic conduction takes place we 

 may congratulate ourselves on the presence here of Professor Quincke 

 and Professor Wiedemann, and we hope to hear something from them. 

 The experiments of Dr. Griadstone, and also some unpublished ones of 

 Professor J. J. Thomson, communicated to the Committee in a letter, will 

 probably be found to have a bearing on this point. 



The question whether there is any radical distinction to be drawn 

 between ordinary compounds and so-called molecular compounds appears 

 to be an open one. Various physical facts lead one to suppose that 

 whereas the ordinary forces of chemical af&nity are strictly electrical 

 there may be other non-electrical forces as well, and that such compounds 

 as are held together by these latter forces are intractable to electrical 

 influence. It is difficult for physicists to understand certain facts (cohe- 

 sion, for instance, and capillarity) without the hypothesis of some non- 

 electrical forces between atoms; but on such a subject as this chemists 

 perhaps ha-? e in their hands evidence which, if at all decided and distinct, 

 would be entitled to great weight. 



The subject of the partition of the current among different electrolytes 

 when mixed together, and the question of the part the solvent plays in 

 the conduction, seem scarcely suitable for discussion at the present stage, 

 because they only require a few rigorous experiments on lines already 

 laid down to settle them. But the editor may just say that, whereas at 

 a former meeting he thought he had obtained experimental evidence that 

 the water conducted some fourth part of the current in certain solutions, 

 he has since found that, using purer substances, and taking exti'eme care 

 to avoid loss of weight by spray, which source of loss is very subtle, this 

 evidence puts on another complexion ; and at the present time he is 

 disposed to coincide more cordially with the orthodox view that water 

 conducts almost as littie when formiogpart of a solution as when existing 



z 2 



