108 Prof. H. E. Armstrong on the Determination of 



abundant evidence to show that in the olefines the carbon 

 atoms are not held together by double bonds. In other 

 words, if we employ Kekule's benzene formula, we are bound 

 to abandon the use of the conventional formula for olefines. 

 From this point of view I see little difference between 

 Kekule's symbol and the prism formula or the modification 

 of the latter quite recently advocated by Thomsen {Deut. 

 them, Ges. Ber, xix. p. 2944). Objections have, however, 

 been urged against the prism formula which appear to be 

 justified ; the symbol advocated by Thomsen can scarcely be 

 regarded as marking any particular advance ; and Kekule's 

 symbol is open to the oft-raised objection that it indicates 

 the existence of four distinct di-derivatives. I venture to 

 think that a symbol free from all objections may be based on 

 the assumption that of the twenty-four affinities of the six 

 carbon atoms twelve are engaged in the formation of the six- 

 carbon ring and six in retaining the six hydrogen atoms, in 

 the manner ordinarily supposed ; while the remaining six 

 react upon each other, — acting towards a centre as it were : 

 so that the " affinity " may be said to be uniformly and sym- 

 metrically distributed. I would, in fact, make use of the 

 following symbol : — 



H H 



C C 



A A 



\/ 



c — c 



H H 



The only difference between this symbol and those employed 

 hitherto arises from the fact that I do not consider that, 

 apart from its connexion with the other carbon atoms owing 

 to their association in a ring, any one carbon atom is directly 

 connected with any other atom not contiguous to it in the 

 ring; my opinion being that each individual carbon atom 

 exercises an influence upon each and every other carbon 

 atom. The idea here expressed is, I believe, essentially diffe- 

 rent from that embodied in the somewhat similar symbol 

 used by Lothar Meyer (Modernen Theorien der Cliemie, ed. 4, 

 1883, p. 262 ; comp. also Briihl, loc. cit. p. 12) : as, according 

 to my view, there is an excess of (negative) affinity beyond 

 what is required to maintain the C 6 H 6 ring ; and as I do not 

 consider that each carbon atom can be supposed to have 

 an affinity free. 



