RECENT ADVANCES IN SCIENCE 543 



Rideal {Trans. Chem. Soc, 1920, 117, 1288) has shown, in a 

 prehminary series of experiments, that the infra-red radiation 

 from the sun or from a hot nichrome wire accelerates the rate 

 of hydrolysis of methyl acetate. The radiation hypothesis is 

 supported by the work of Cox {Trans. Chem. Soc, 192 1, 119, 142) 

 and Dhar {Proc. K. Akad. Wetensch., Amsterdam, 1920, 23, 308). 

 These two authors have investigated the temperature co- 

 efficients of certain reactions. Cox finds that the temperature 

 coefficient of a reaction in the various solvents is inversely 

 proportional to the velocity in the solvent — a condition which 

 is required by the radiation hypothesis. 



The " Cyanogen " Bands.. — Barratt {Proc. Roy. Soc, 1920, 

 A 98, 40) has investigated the problem of the source of these 

 bands. It was formerly considered that the cyanogen bands 

 were produced by a compound of carbon and nitrogen, but 

 Grotrian and Runge in 1914 threw doubt on this conclusion. 

 In experiments with Schonherr elongated arcs they found that 

 the cyanogen spectrum was produced with metal electrodes and 

 nitrogen alone. On the other hand, Hemsaleck obtained 

 evidence that nitrogen is not essential to their formation. These 

 contradictions are readily explained, since the presence of carbon 

 and nitrogen in very small quantities suffices to produce the 

 bands. Barratt has examined the spectrum of a number of 

 flames, and has found that the cyanogen spectrum is only 

 present in those containing carbon, nitrogen, and hydrogen. 

 The nitrous oxide-coal gas flame yielded these bands, whereas 

 the nitrous oxide-hydrogen flame did not. Elementary nitrogen 

 is not so efficient as combined nitrogen, and the presence of 

 oxygen is unfavourable to the production of these bands. This 

 spectrum offers a very sensitive test for the presence of carbon 

 and nitrogen in gases, and in the case of carbon is much more 

 sensitive than any other carbon lines. 



Luminescence. — Schmidt {Ann. Phys., 1920, [iv], 63, 2 4) 

 continuing the work of Lenard and others on the phosphores- 

 cence of the alkaline earth substances, has investigated the 

 oxide phosphoroids. Lenard showed that a phosphoroid should 

 be of the type sulphide — easily fusible salt — heavy metal. 

 The quantity of the heavy metal present should not exceed 

 io~* times that of the sulphide. Pauli and Hirsch have shown 

 that sulphides may be replaced by oxides or selenides without 

 the mixtures losing their phosphorescent properties when 

 exposed to light. Schmidt has examined the luminescence and 

 phosphorescence of the oxide class of substances when exposed 

 to light of wave-lengths ranging up to 220/ui/j,. Certain wave- 

 lengths in the blue and ultra-violet were shown to excite 

 phosphorescence to the maximum extent. The wave-length 

 of both the exciting and incited radiation was found to be 



