220 JONES-STRONG— THE ABSORPTION SPECTRA [April 24, 



phosphorescent spectrum (14) should be studied in this connection, 

 especially as affected by the mode of stimulation (X-rays, cathode 

 rays, heating or monochromatic light of different wave-lengths). 

 The temperature, electric or magnetic field could be changed about 

 the phosphorescing body. The effect of change of state (15) 

 should be tried if this is possible, also any possible changes of 

 valency of the atoms (16) composing the body investigated. We 

 shall attack the problem from all of these standpoints. 



After correlating the data obtained by the above named in- 

 vestigations it is pretty certain that it will be possible to take each 

 vibrator and trace the effects produced upon it by the above changes. 

 It is also quite certain that we shall also know something of the 

 nature of the vibrating system and the part that it plays in that 

 complex body we call the atom. We shall now describe a few 

 results obtained by changing the concentration and temperature of a 

 solution of the chemical compound whose absorption spectrum we 

 are studying. 



IX. The Effect of Rise in Temperature on the Absorption 

 Spectrum of Certain Salts in Aqueous Solution. 



(a) Uranous Chloride (B, Plate VII.). 



To a normal solution of uranyl chloride in water was added a 

 small amount of hydrochloric acid and zinc. The production of 

 hydrogen reduced the uranyl to the uranous state. The same can 

 be done in some cases by simply passing hydrogen gas through the 

 uranyl solution. The solution was placed in the glass trough and a 

 temperature run made as in the usual manner. The thickness of 

 layer was i mm. The length of exposure was 50 sec. to the 

 Nernst glower and 4 mins. to the spark, the current through the 

 glower being 0.8 amperes and the slit width 0.20 mm. Starting 

 with the strip nearest the comparison scale the temperatures were 

 8°, 17°, 33°, 48°, 62° and 73°. An exposure was also made at 

 80° which is not shown in the spectrogram B. 



At 8° a mist formed on the prisms and for this reason the spec- 

 trum film taken at this temperature is much underexposed and the 

 bands appear wider than at the higher temperatures. At this tem- 



