FROZEN SOLUTIONS. 



183 



cence band. Jones and Strong employed the continuous spectrum of 

 the Nernst lamp, which produces fluorescence in this region. Such 

 luminescence, although masked by the more intense background, 

 tends to shift the crest of the absorption band toward the violet. 



A comparison of the wave-lengths of the bands of the solid with 

 those of the solution indicates a progressive difference. When the 

 spectra of the solution and of the solid are plotted in frequency units, 

 either is found to include only one series of bands, those of the solution 

 being of a slightly smaller interval than those of the solid. 



TABLE 108. Uranyl sulphate in water. 1 



1 The numbers by which unresolved bands are designated in this and the following tables 

 correspond to the group numbers used in previous chapters, since each band corresponds to a 

 group in the resolved spectra of the crystallized salts. 



In figure 91, band 5 is seen to shift with falling temperature toward 

 the violet, the shift amounting to 13 A.u. when a temperature of 

 100 is reached. With further cooling to 180 the band shifts back 

 toward the red. It would be interesting to ascertain whether this shift 

 toward the red would continue with further decrease in temperature. 

 The other bands of the normal solution behave similarly with falling 

 temperature, i. e., the entire spectrum undergoes a shift to the violet, 

 followed by a reverse shift to the red. The wave-lengths of the bands 

 at 180 are approximately the same as the wave-lengths at 60. 



