302 Scientific Intelligence. 



separates germanium from all the other metals and semi-metals. 



It was found, however, that arsenic and germanium can be 

 quantitatively separated by the action of hydrogen sulphide upon 

 solutions of their oxides in the presence of a large excess of hydro- 

 fluoric acid, for under these conditions the arsenic is precipitated 

 while the germanium is not affected. A series of test analyses 

 made with known quantities of the two elements gave most excel- 

 lent results by this method. — Jour. Amer. Chem. Soc, 43, 2549. 



h. l. w. 



5. Asymmetry of the Gaseous Molecule. — According to the 

 theory developed by the late Lord Rayleigh, the color of the blue 

 sky may be explained by light which is scattered by the gaseous 

 molecules of the air, and, according to the simple theory, if the 

 molecules were spherical this scattered light should be completely 

 polarized. It was suggested by R. J. Strutt, the present Lord 

 Rayleigh, that any departure from complete polarization would 

 indicate that the molecule had certain preferential directions of 

 vibration. Experiments designed to test the degree of polariza- 

 tion were devised by Strutt in 1919 and showed that none of the 

 seventeen gases and vapors examined exhibited complete polariza- 

 tion of the scattered light. This was what might have been 

 anticipated, for the modern view of the structure of atoms would 

 not lead us to expect that the atom would behave as if possessing 

 spherical symmetry, even apart from the grouping of the atoms in 

 the molecule. 



The gas under examination was placed in a metal tube with 

 crossed arms which were properly blackened on the inside. A 

 strong beam of light was sent through one of the arms and the 

 scattered light was viewed through a double image prism in the 

 end of the transverse arm. One of these images contained the 

 scattered light which had been polarized and whose vibrations 

 were perpendicular to the traversing beam, while the other con- 

 tained light belonging to the unpolarized portion and on emer- 

 gence possessed vibrations parallel to the original beam. To com- 

 pare the intensities of these images, w T hich were widely different, 

 a set of absorbing films of varying opacity was prepared. These 

 were interposed in the path of the stronger beam and the two 

 images photographed side by side. When the result showed two 

 images of sensibly the same intensity it was possible from the 

 calibrated scale of the absorbing diaphragms used to estimate the 

 relative intensities of the polarized and the unpolarized light. 



These investigations of Strutt have now been repeated and 

 considerably extended, with various improvements in the form of 

 the apparatus, by R. Gans. The degree of asymmetry may be 

 represented to the eye by constructing an ellipsoid of revolution, 

 but with the understanding, of course, that this is in no sense to 

 be identified with the actual contour of the molecule. The author 



