PROGRESS IN PHYSICAL CHEMISTRY. 303 



The rotatory powers of salts of o-bromcamphoric acid 

 when equally dissociated are found by Walden to be the 

 same ( 1 30) ; if two active ions be present the rotatory power 

 is found to be the sum of the rotatory powers of each. 

 Carrara (131) also shows that the rotation of salts of 

 nicotine conforms to the dissociation theory, and more 

 striking support still is furnished by Blosfeld (132). If an 

 equivalent of a strong acid be added to a solution contain- 

 ing an equivalent of asparagine, the rotation is altered to 

 about the same extent no matter what acid be used ; this 

 is no longer true, however, with weak acids. The explana- 

 tion is that the strong acids form salts which are not 

 hydrolysed and are almost completely dissociated ; the rota- 

 tion in equivalent solutions is, therefore, due to the same 

 number of active ions and is the same for all. With weak 

 acids hydrolysis occurs, and the dissociation and hence the 

 rotation varies in each case. 



The rotation of rhamnose in isopropyl alcohol is positive 

 but is negative in ethyl alcohol. From observations on the 

 boiling-point, Sale (133) finds that in ethyl alcohol the 

 molecular weight is too high. 



The rotations of solutions in chloroform of position 

 isomers, chiefly derivatives of phenyl carbamic acid, show, 

 according to Goldschmiclt and Freund (134), that in general 

 the value of the meta-compound is intermediate to those of 

 its ortho- and para-isomers. Kannonikoff (134) has tried to 

 prove experimentally that a, the angle of rotation in a 200 

 mm. tube of a solution of an active substance is connected 

 with 0, the angle of minimum deviation in a 6o° prism, by 

 the relation a = A<j> + B. A and B are constants varying 

 with the solvent, but A/B is nearly the same for different 

 substances dissolved in the same solvent. He considers 

 that A/B is closely related to the chemical nature of the 

 solvent, and may be used as an aid in determining its 

 constitution ; his data, however, are in some cases not very 

 satisfactory. 



Perkin (135) has confirmed his previous conclusion that 

 the magnetic rotation of hydrogen chloride in dilute aqueous 

 solution is almost twice as great as when it is dissolved in 



