Optical Isomerism, and the /\in;/- Elect ran. 439 



pressure, and concentration presents difficulties whatever view 

 may he adopted as to the origin of the rotation. The suhject 

 has been discussed by Livens *, who has examined the effect 

 of the presence o£ inactive substances, as in the case where a 

 simple active substance is dissolved in an inactive liquid, and 

 also by Gray f. Assuming that the atoms are vibrating about 

 points of equilibrium inside the molecule, the average value 

 of both the electrostatic and the magnetic field produced will 

 change with the amplitude of the oscillations, and conse- 

 quently the degree of asymmetry will be a function of the 

 temperature. 



Finally, it may be noted that the optical activity of 

 compounds containing asymmetric atoms other than carbon 

 atoms follows at once from the theory. Such active 

 compounds are known in the case of nitrogen, phosphorus, 

 sulphur, selenium, tin, silicon, cobalt, chromium, rhodium, 

 and iron 1. It is perhaps not without significance that the 

 three elements cobalt, rhodium, and iridium occupy a 

 peculiar position in Langmuir's theory, as in each case there 

 is an odd electron in the outer shell which is assumed to 

 occupy a position at one end of the polar axis. 



Summary and Conclusion. 



In the present paper a theory of optical rotation has been 

 advanced in which the electron, instead of being regarded as a 

 point charge, is looked upon (as suggested by A. L. Parson) as 

 an anchor ring of negative electricity rotating rapidly about 

 its axis. Such a ring-electron vibrating in a linear path takes 

 the place of an ordinary electron moving in a spiral path as 

 postulated by Drude. It is shown that rotation of the plane 

 of polarization of light will result, and an expression is 

 found for the amount of rotation per unit length. Employ- 

 ing the theory of atomic structure due to Lewis and 

 Langmuir, a graphical representation may be obtained for 

 dextro- and l?evo-rotatory forms of a compound. The ex- 

 perimental facts with regard to optical activity are in good 

 agreement with the theory put forward, which may be 

 applied not merely to carbon compounds, but to any com- 

 pound containing an asymmetric atom. 



* Livens, Phil. Mag. vol. xxv. p. 817 (1913). 



t Loc. cit. 



\ A. TV. Stewart, ' Stereochemistry," chapter x. (1919). 



