702 



SCIENCE PROGRESS 



a and b^ c and d^ e and /; or alternatively between b and c, 

 d and e. The units of two kinds formed are, however, identical. 

 When, however, some of the spheres representing hydrogen 

 are removed and others introduced in accordance with one of 

 the various cases of chemical substitution, the two kinds of 

 partitioning sometimes produce different isomers, the difference 

 consisting in some cases of an enantiomorphous relation, in 

 others amounting to a more remote isomerism. In regard to 

 cases in which partitioning in the two different ways gives two 

 kinds of units enantiomorphously related, the fact that the 



Fig. s. 



existence of this possibility has not yet been experimentally 

 verified may be attributed to the law of chances, since par- 

 titioning of both kinds will take place to an equal extent. The 

 resulting enantiomorphous derivatives will be externally com- 

 pensated. Perhaps some day they will be disentangled and 

 thus their existence established. 



To compare the benzene units obtained by partitioning with 

 the usual hexagon formula of the hydrocarbon, we have to 

 remember, in the first place, that but one mono- substitution 

 product can be formed by substitution of one hydrogen atom 

 in each alternate layer of the columns. As to those obtained 

 by further substitution : in fig. 5 the hydrogen atoms are 



