374 Prof. H. E. Armstrong on Low-Tewperature Research 



The conventional ring formulae assigned to the benzenoid hydro- 

 carbons, such as have been used above, however, are expressions 

 which are to be regarded as symbolic of the functions of such sub- 

 stances rather than as absolute representations of their structure. 

 Thus the simple hexagon by which benzene is represented above is 

 symbolic of a symmetrical closed system. In representing naphtha- 

 lene merely by two conjoined hexagons therefore, expression is 

 given to the fact that it also functions as a symmetrical closed 

 system. Actually, it must be supposed that it is impossible — 

 assuming that benzene has a centric structure — to fuse two benzene 

 rings together and yet preserve the centric structure of ])oth. If 

 theaffinities of the carbon atom operate in any rigid manner " tetra- 

 liedrally," the ten carbon atoms of naphthalene must form a con- 

 stricted monocycloid system, thus — 



As the affinities at the waist of this system merely interlace, they do 

 not satisfy each other ; hence the unsaturated character of the mole- 

 cule is represented by this formula, whilst at the same time naphtha- 

 lene is shown to possess a special character of its own. Such a 

 formula is in close accord with the general chemical behaviour of 

 the hydrocarbon. 



Anthracene, Ci^Hio, may be modelled in carbon affinities in two 

 ways, one of which is symmetrical and the other unsymmetrical: — 



Tne first in no way corresponds to the properties of the hydro- 

 carbon : the second, however, both gives expression to its unsym- 



