1913] on Applications of Polarized Light 737 



The uext step was obviously to try to arrest the isomeric change 

 by the addition of carbonyl chloride to a solvent which did not 

 naturally contain it. This was done with marked success. A 

 solution of nitrocaniphor in purified ether showed a change of 

 rotatory power extending- over about a day ; by the addition of 

 carbonyl chloride the period was increased to eighteen days in a glass 

 vessel, and to sixty-one days when a silica vessel (free from alkali) 

 was used to contain the solution. In the case of benzene, to which 

 acetyl chloride Avas added, the period was increased from sixteen days 

 to sixty-four days in glass, and to two years in a silica vessel. Finally, 

 by the addition of carbonyl chloride to a solution of nitrocamphor in 

 benzene contained in a silica vessel the period was increased from 

 sixteen days to six years. 



Action of Light. 



A convenient method of studying the effecL of light on isomeric 

 change has recently been devised in which the polarimeter plays a 

 leading part. The solution to be studied was enclosed in a silica tube, 

 surrounded by a silica water-jacket, and exposed to the light from a 

 silica mercury lamp. In seven cases out of nine, however, no accelera- 

 tion whatever could be detected as a result of this extremely powerful 

 "insolation." 



I have attempted to give some account of a few instances in 

 which polarized light has been applied to the solution of chemical 

 and physical problems. In each case the observations have taken the 

 form of measurements of rotatory polarization. Measurements such 

 as these have supplied to the chemist a key which has enabled him to 

 unlock the strong-room in which many of the secrets of molecular 

 structure were stored. The physicist, too, following in the footsteps 

 of Faraday, has found in rotatory polarization a link between the 

 sciences of magnetism and optics, and has obtained valual^le hints 

 as to the way in which light is propagated through matter. The 

 hundred years which have elapsed since Biot announced his great 

 discovery have therefore served only to enhance its brilliance, and to 

 reveal it as one of the most illuminating disclosures even of the 

 splendid period in which it was made. 



[T. M. L.] 



