24 SCIENCE PROGRESS 



shows a progressive intensification of the secondary line 

 spectrum, which is probably due to this triatomic form. Wendt 

 disagrees with the suggestion of Baly that hysone is probably 

 the same as the iso-hydrogen of Harkins. It is certainly not 

 an isotope of Hg since its boiling-point is at least 70° C. above 

 that of hydrogen. Newman {Phil. Mag., 1922, 43, 455) finds 

 that a-rays produce active forms of hydrogen and nitrogen at 

 moderately high pressures — 300 mm. These react with many 

 elements, particularly with the fresh surfaces of metals. The 

 a-rays produce atoms on collision, which probably unite with 

 unchanged molecules to give the triatomic forms, Zenneck 

 {Phys. Zeit., 1921, 22, 102) describes a method of producing 

 the afterglow of active nitrogen by an electrodeless ring 

 current. 



Photochemical Processes. — Recent work on phosphorescence 

 confirms the Lenard theory. On this theory, during illumina- 

 tion of the phosphorescent substance by the exciting light 

 electrons are emitted from the active centres. The con- 

 ductivity of the phosphor should thus increase on illumi- 

 nation. Godden and Pohl {Zeit. Physik., 1920, 3, 98), using 

 a calcium-bismuth-sodium phosphorescent substance, find 

 that the maximum conductivity is obtained when the 

 phosphor is exposed to the light which produces the maximum 

 excitation of the phosphorescence. On the other hand, during 

 the interval of emission of phosphorescent light, no conductivity 

 due to the return of the electrons was detected. An increase in 

 conductivity was, however, noted when the excited body was 

 exposed to infra-red light, which accelerates the return of the 

 electrons. 



The relationship between ionisation and the decomposition 

 of organic dyes by light has been studied by Lazareif {Zeit. 

 Phys. Chem., 1921, 98, 94). His view of the action of light in 

 photochemical processes, is that in some of the light-sensitive 

 molecules an electron is activated by passing to an outer 

 Bohr orbit. This causes a virtual increase in the size of the 

 atom or molecule, and a light-sensitive gas mixture should 

 undergo an increase in volume when illuminated. This 

 phenomenon was observed by Bunsen and Roscoe and more 

 recently by Baly and Barker in the case of gaseous mixtures 

 containing chlorine. Lazareff has shown that the bleaching of 

 organic dyes in the presence of oxygen up to 150 atm. obeys 

 the law 



dc 

 dt 



— -T. =ao{i — e-^") (i — e-**''^. 



R. W. Wood {Phil. Mag., 1922, 43, 757) has investigated 

 the action of light on fluorescent substances to test the theory 



