354 TRANSACTIONS OF SECTION B. 



the ionisation being normal, the recombination abnormal. And in the third 

 form we have 



dt ~ Ui 



at 



the ionisation being abnormal and the recombination normal. 



Now, if it were possible to measure directly the velocity of either ionisation 

 or recombination, we should at once be able to select the equilibrium formula 

 which was really applicable. Unfortunately such velocities are so high as to 

 be beyond our powers of measurement. Yet it seems possible to seek and obtain 

 an answer from reaction velocities which are measurable. One assumption must 

 be made, but it seems to me so inherently probable that few will hesitate to 

 make it. It is this, if a substance in a given solution has normal activity with 

 respect to one reaction, it has normal activity with respect to all reactions in 

 which it can take part in that given solution. Similarly, if a substance in a 

 given solution exhibits abnormal activity with respect to one reaction, it will 

 exhibit abnormal activity with respect to all. 



Granting this assumption, we have then to find a reaction in which either 

 the ionised or un-ionised portion of an abnormal electrolyte is converted into a 

 third substance with measurable velocity. Such a reaction exists in the trans- 

 formation of ammonium cyanate into urea in aqueous and aqueous-alcoholic 

 solutions, which was investigated some years ago by myself and my collaborators, 

 and found to proceed at rates which could easily be followed experimentally. 

 First of all comes the question : Is the urea formed directly from the ions or 

 from the unionised cyanate ? As Wegscheider pointed out, it is impossible from 

 reaction-velocity alone to determine which portion passes directly into urea, if 

 the velocities of ionisation and recombination are infinitely greater than that of 

 the urea-formation, as is undoubtedly the case. Other circumstances make it 

 highly probable that the ions are the active participants in the transformation, 

 but we may leave the question open, and discuss the results on both assumptions. 



Suppose, first, that the un-ionised cyanate is transformed directly into urea. 

 Then we have the successive reactions 



NrL/-fCNO' ~^t NH 4 CNO > CO(NH 2 )., 



The slight reverse transformation of urea into cyanate may for the present pur- 

 pose be neglected, a6 it in no way influences the reasoning to be employed. 



If the un-ionised substance behaves normally, then the conversion of the 

 ammonium cyanate into urea, when referred to the un-ionised substance, will 

 appear unimolecular and obey the law of mass-action : when referred to the 

 ionised substance it will not appear to be bimolecular and will not obey the law 

 of mas6-action. 



Suppose, now, that the direct formation of the urea is from the ions. Then 

 we are dealing with the actions 



NH 4 CNO — ^ NH 4 - + CNO' > CO(NH 2 ),. 



Again, let us assume the unionised substance to be normal. Once more, if the 

 transformation is referred to the non-ionised substance it will appear as mono- 

 molecular; when referred to the ionised substance it will not appear as bimole- 

 cular, as it should if the mass-action law were obeyed.. 



It is a matter of indifference, then, so far as the point with which we are 

 dealing is concerned, whether the ionised or the non-ionised cyanate is trans- 

 formed directly into urea. If the non-ionised cyanate behaves normally the 

 action when referred to it will in either case appear to be strictly monomolecular. 



If the ionised cyanate, on the other hand, behaves normally, the reaction 

 when referred to it will be bimolecular and normal; when referred to the non- 

 ionised cyanate it will not be monomolecular, and therefore will be abnormal. 



The actual experiments show that whether water or a mixture of water and 

 alcohol be taken as solvent, the reaction when referred to the ions is strictly bi- 

 molecular ; when referred to the non-ionised substance it is not monomolecular, 



