Manchester Memoirs, Vol. Ixiv (1920), No. 4 



IV.— The Conjugation of Partial Valencies. 

 By Professor Robert Robinson, D.Sc., F.R.S. 



(Bead March 16th, 1920. Received for publication August 9th, 1920.) 



During the past five years the author has made use of a 

 hypothesis which has appeared to simplify the representation 

 of the possible mechanism of reactions in certain isolated 

 cases, and the object of the present communication is to 

 indicate some of the lines along which the theory may receive 

 more general application. The necessary condition precedent 

 to chemical change is assumed to be the " activation " of one 

 or more of the molecules taking part in the reaction; this is 

 followed by cohesion and rearrangement of valencies, most 

 probably synonymous with changes in position of electrons. 

 The result is either molecular rearrangement, the formation 

 of an additive product or of new substances by fission of the 

 complex. The activated molecules are further assumed to be 

 polarised and to contain partially dissociated valencies. Thus 

 H -CI is supposed to be chemically inert, the molecule absorbs 

 energy and becomes . . . . H . . . CI . . . which is the 

 reactive form termed partially dissociated because it is a stage 

 towards complete ionisation. In thus splitting a valency it 

 is always understood that the tw T o or more dotted lines, though 

 not necessarily themselves of equal value, are quantitatively 

 equivalent in the sum to the normal unit valency from which 

 they have been derived and the polar character of all these 

 fractional valencies is identical. It is possible to allocate 

 definite signs to the partial valencies in most cases as the 

 result of a consideration of the relative polarities of atoms 

 evinced for example in the limiting case of true electrolytic 

 dissociation. A significant exception to the rule that partial 

 valencies of similar sign emanate from the same atom at the 

 same time exists in the case of those elements which exhibit 

 latent valancies such as trivalent nitrogen. A neutral nitrogen 



atom is represented thus: — — N^ 



/ 

 March 22nd I, IQ21. 



