82 



The direction of the rotation of the iientral barium salts is, as 

 in the case of sulphopropionic acid, opposite to that of the free acids. 



The molecular rotatory power de|)end8 on the concentration; on 

 dilution it rises a little. The barium salts, for instance, give in a 

 2i °/o solution for sodium light a molecular rotation of 32.2° and 

 in a 57» solution a rotation of 29.9°. In a 2^ 7» solution the presence 

 of 10°'„ of barium chloride lowers the molecular rotation to 29.3°. 



This indicates, that the rise of the molecular rotation on dilution 

 may be ascribed to an increasing of the ionization, a phenomenon, 

 which is perhaps coimected with the fact that the sign of rotation 

 of the neutral salts is opposite to that of the free acids. 



The molecular rotation of the free salts for sodium light is 7.8°. 



The i^cid salts rotate the plane of polarisation in tiie same direction 

 and to about the same amount as the free acids. 



In this respect also, the behaviour of sulphobutyric acid is there- 

 fore analogous to that of sulphopropionic acid. 



The investigation is being continued and will be published later 

 in greater detail. 



Groningen. 13 Jan. 1923. Organic Chemical Laboratory of 



the University. 



