400 Scientific Intelligence. 



and a single 60° prism of the last named material. The absorp- 

 tion cell and the general assemblage of apparatus Avere set up in 

 the usual manner. As already implied, the positions and inten- 

 sities of the bands were recorded photographically. 



The maxima of the absorption bands of acetone are shown by 

 the curves to have the approximate wave-lengths 275//./* and 

 355 /x/x respectively. The fluorescence bands extend from 260 fx/x 

 to 320 fji/x and from 325 fx/x to 460 fxfx. The former has a minimum 

 of emission at 300 fxfx and the latter at 340 fxfx. In other words, 

 each fluorescent band seems to be double. For the concentration 

 used, "1:320", the greatest intensity of fluorescence falls at 

 360 /x/x. For diacetyl the maxima of absorption lie at 285 fxfx and 

 410/x/x. The shorter wave-length fluorescent band is also double 

 and comprises the interval 270 fxfx to 350 fi.fi, the minimum being 

 shown graphically at 320^. The longer wave-length fluorescent 

 band is single and extends from about 355 fxfx to 480 fxfx. The 

 fluorescent maximum comes at 410/x/x for a concentration of 

 1:620. For ethylencyanid-monoxal-ethylester the maxima of 

 absorption have the wave-lengths 335 /x/x and about 430 fx/x. Both 

 fluorescent bands are single, the one extending from 290 fxfx to 

 365 fj.fi, and the other from 395 fx/x to below 480 fx/x. For the con- 

 centration employed, 1:1 J 200, the intensity of emission is greatest 

 at 435 fifi.. 



The three ketones satisfy the requirements for " coupled " 

 bands. That is, when the wave-lengths of the exciting light lie 

 within the more refrangible absorption bands, both fluorescent 

 bands come out strongly, provided, of course, the concentration 

 is appropriate for observation. On the other hand, fluorescence 

 is not appreciably produced when the wave-lengths absorbed are 

 confined, to the region of the less refrangible absorption bands. 

 Although the absorption is much greater in the short-wave than 

 in the long-wave bands, nevertheless the more refrangible fluo- 

 rescence is markedly less intense than the less refrangible fluo- 

 rescence. This is doubtless due to the excessive absorption of the 

 shorter wave-length fluorescent light by even thin layers of the 

 solution. According to Stark's theory, the " centers " of the 

 absorption and fluorescent bands of the substances under 

 consideration are the valence electrons of oxygen which are 

 loosely bound to carbon. — Physikal. Ztschr., No. 13, July, 1912, 

 p. 584. h. s. tr. 



7. JDie lonisierung von Gasen durch Licht und das Funken- 

 spektrum des Aluminiums im Gebiete der Schumannstrahlen. — 

 Certain spectrograms taken by Theodore Lyman have enabled 

 him to bring out some interesting and important facts relating to 

 the spectra of the sources of light used by Lenard and others in 

 the study of the ionization of gases by ultra-violet light. The 

 region under consideration extends from wave-length 1200 A. IT. 

 to about 1870 A. U. The first positive reproduced shows the 

 spectrum of a spark between aluminium electrodes in an atmos- 

 phere of hydrogen. A comparatively small number of lines 



