132 



image of the first, inust be present, because the reflection of the 

 elementary volume A in the symmetry-plane will change it into 

 its contiguous, but in general non-superposable mirror-image A', 

 etc. Within all such enantiomorphously related fundamental domains 

 the whole distribution of matter must of course also be enantio- 



morphous; and this is the 

 meaning of the supposition of 

 Von Fedorow and Schoen- 

 flies, when they maintain 

 that crystals possessing sym- 

 metry-properties of the second 

 order must be built up . by 

 certain atom-complexes (cry- 

 stal-molecules) which are of 

 two, enantiomorphously rela- 

 ted, kinds. Only in the cases 

 of enantiomorphous crystals 

 the righthanded and left- 

 handed crystals can separate- 

 ly be composed by atom- 

 complexes of one and the 

 same kind, right or left- 



<C> O 



.r% ^-^ <r 



r-> ^ r-> ^-, r-> 



? A7 A? 



Fig. 1 1 8. 



handed. If such crystals as, 



for instance, those of dextro- and laevogyrate sodium-chlorate, are 

 dissolved, giving an optically wactive solution, the supposition 

 must necessarily be made that a re-arrangement of the atoms during 

 the process of dissolution takes place, producing an equal number 

 of both kinds of enantiomorphous molecules, or perhaps a quite 

 different species of them, superposable with their mirror-image. This 

 is intimately connected with the fact that the notion of the funda- 

 mental domain is a purely mathematical one, and therefore with 

 respect to the endless periodical repetition of equal parts throughout 

 the regular structure, the gathering together of certain atoms into 

 complexes, is within wider limits a quite arbitrary, purely mathema- 

 tical fiction. The notion of "molecular complex" is in the crystalline 

 state therefore formally without significance; which however does 

 not mean that the connections between the constituting atoms, as 

 involved in the study of the properties of the chemical molecule, 

 should have completely disappeared (See p. 153). Only they need not 

 be considered for the mathematical description of the crystalline, 



