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acetate 1 ), etc., are dissolved in water, the optical activity entirely 

 disappears. From this the conclusion has often been drawn, that 

 the optical activity is merely due to the spiral arrangement of the 

 crystal-molecules, this involving a laevo-, respectively a dextro- 

 gyratory helicoidal assemblage, which breaks down as soon as the 

 crystals are dissolved 2 ). 



However, Barker and Marsh 3 ) have recently drawn attention 

 to the fact that among these substances there are a number, 

 which should have binary helicoidal axes, especially those belong- 

 ing to the rhombic and monoclinic system. Such assemblages 

 should only exhibit true enantiomorphism if the constituting 

 units of the structure have themselves a non-superposable sym- 

 metry 1 ). According to these authors, this will apply to such cases 

 as sodium-chlorate and -br ornate, because their heteropolar ternary 

 axes are always combined in pairs. They conclude from their 

 reasonings, that molecules such as NaCl0 3 , MgSO^-\-7H 2 } etc., 

 must themselves have an enantiomorphous configuration. 



To gain such a conception of the stereometrical configuration 

 of inorganic salts such as the above mentioned, the authors take 

 into account Werner's coordination-schemes. As might, however, 

 be expected in advance, they only succeed in finding such stereo- 

 chemical formulae in a few cases; thus in the case of magnesium- 

 sulphate (+7 Hff), and of sodium-chlorate, while in far the most 

 cases too little is known about the true constitution of the salts 

 considered, to make such an attempt successful. Even in the 

 case of the two salts mentioned, their suppositions seem rather 



J ) For so dium-ur any I- acetate, however, the pseudosymmetrical character seems 

 also to be proved beyond any doubt. 



2 ) It was discussed, however, by the author (Proceed. Kon. Acad. Amsterdam, 

 Vol. 20, 268, (1917); Chem. Weekblad, 14, 723, (1917), that in systems of trueanti- 

 podes sometimes phenomena may be observed, which are completely analogous to 

 those found in the case of sodium-chlorate; etc. The optically active forms of 

 potassium-rhodium-trioxalate show abnormal rotation-dispersion, their specific 

 rotation passing through zero for a wave-length of 5970 A. U. For light of this 

 special wave-length the ternary system of solvent and both antipodes behaves in 

 apparently the same way as the binary system built up from the components: 

 solvent + sodium- chlorate. This is valid, however, only for that one, singular 

 point of the system, and only for a definite temperature and pressure. 



3 ) Th. V. Barker and J. E. Marsh, Journ. of the Chem. Soc. London, 103, 

 837, (1913). 



4 ) Cf.: St. Kreutz, Elemente der Krystallstruktur, I, p. 83,90, (1915). 



