of the Constitution of Carbon Compounds. Ill 



whereas his results, when studied from the present stand- 

 point, not only confirm it, but endue it for the first time with 

 a clear kinetic meaning. 



Passing on to other cases affected by the introduction of x% 

 it will be seen that the union of the carbon atoms in the 

 (hypothetical) gaseous molecular carbon by single bonds only, 

 and the non-existence of the fourfold bond, is no longer 

 tenable; and that the whole basis of the argument on which 

 the surprisingly small values for the formation of molecular 

 nitrogen and molecular oxygen rest is thus destroyed, and the 

 conclusions which are based on these quantities, in some cases 

 so opposed to all accepted views, will be destroyed also. 



#, however, will not affect the values calculated for the heat 

 of formation of benzene, except in so far as the difference in 

 these values will be comparatively a much more insignificant 

 quantity than formerly. But the difficulty experienced in 

 adopting Kekule's formula will vanish if we accept in its en- 

 tirety the kinetic conception of bonds here developed. All that 

 Thomsen has proved is that in certain classes of compounds — 

 so-called open-chain bodies — v 2 is somewhat less than twice v Y ; 

 but it by no means follows that, in compounds constituted on 

 such a different principle, and possessing such perfect sym- 

 metry as benzene, this should be the case : in benzene the 

 second bond has probably the full value of the first bond, 

 v 2 =2v 1 , and hence the stability of the substance. The con- 

 ception that the value of a bond, between even the same 

 atoms, has a somewhat variable value dependent on the nature 

 of the other atoms present in the compound, has already been 

 developed in another direction by the author (" Atomic 

 Valency," Chem. Soc. Proc. 1885, p. 122), and has been in- 

 dependently brought forward by Professor Armstrong, and 

 used by him to explain many of the apparently anomalous 

 results arrived at by Thomsen in other parts of the work 

 under discussion. 



As with the value of r, so also with the heat evolved on the 

 combination of a chlorine atom with carbon and of hydroxyl 



rn 



with carbon, Thomsen's numbers will have to be increased by j 

 for each CI or (OH). With the ethers, the value assigned to 

 C— — C will be T greater ; in the aldehydes, H — C=0 will 



become -j- greater; in the ketones HC=0 will be ^ greater; 



3x 

 and in the acids 0=C — OH will become -j greater*. 



* In all these cases the numbers represent the heat of formation from 

 gaseous atomic carbon and the other elements in the molecular condition. 



