282 



a pentavalent, asymmetric nitrogen-atom which, as we have seen, 

 can in many cases exhibit a true molecular dissymmetry (p. 241). 

 There is some probability here, therefore, that the explanation 

 suggested above is valid in this case, and the great analogy of this 

 behaviour with that of the sodium-chlorate-crystals could also 

 easily persuade us to adopt in the last case a similar inter- 

 pretation of the phenomenon, as might be given for the piperi- 

 donium-deriva.tive . 



In any case it seems worth while to keep these facts in mind, 

 and to gather more instances before rejecting completely the ideas 

 discussed above. 



30. If we review once more, what the considerations dealt 

 with in this chapter have led to, we may say that the meaning 

 of Pasteur's famous law has become appreciably clearer after 

 all the investigations of the last decenniums, than it must have 

 appeared at the time when it was first formulated by the great 

 French discoverer. We may perhaps state these results in the 

 most concise way by summarising the typical features as follows : 



1). An atomic arrangement in chemical molecules which has 

 only axial symmetry, involves the property of a possible fission 

 into enantiomorphously related isomerides endowed with optical 

 rotatory power. 



2). If a chemical compound possesses a single asymmetrical 

 plurivalent atom (^>3) in the sense of Van 't Hoff and 

 Le Bel's theory, all conditions are present to make the com- 

 pound resolvable into such enantiomorphously related isomerides 

 endowed with optical rotatory power. 



3). The possibility of a fission as indicated is, however, not 

 necessarily restricted to the special case of the existence of 

 an asymmetrical plurivalent atom; it is, contrary to this view, 

 merely dependent upon the presence of a stereometrical configura- 

 tion* which has only axial symmetry, and this may also occur if 

 no asymmetric atoms whatsoever, in the sense of Van 'tHoff 

 and Le Bel's theory, be present. Conversely: even if several of 

 such asymmetric atoms be present in the molecule, it may 

 occasionally be optically wactive and non-resolvable into enantio- 

 morphous antipodes. 



4). The magnitude of the optical rotation seems to be deter- 

 mined much more by the configuration in space, than by the chemical 

 contrast between the substitutes; the nature of the plurivalent 



