FROZEN SOLUTIONS. 



195 



manipulation of the cooling process, be made to yield either an unre- 

 solved or a highly resolved spectrum. The intermediate forms were 

 not easy to reproduce at will. A comparison of the wave-lengths of the 

 strongly resolved bands of the solution at 180 with those of the 

 crystalline salt at the same temperature showed that they were identical. 

 The uranyl ammonium nitrate and uranyl potassium nitrate in 

 aqueous solution were similarly cooled and showed resolution of the 

 same type. Resolution of this type has not been discovered in any 

 other aqueous solutions, but in our first investigation uranyl acetate 

 in alcohol was found to give highly resolved but quite dim bands 

 superimposed on a continuous background. The spectra of the 1/100 

 normal solution were similarly affected by retarding the rate of cooling. 

 Spectra L, M, and N of figure 96 show the results of successively slower 

 rates of cooling. 



EFFECT OF TEMPERATURE ON SLOWLY COOLED SOLUTIONS OF URANYL 



NITRATE. 



Since the changes in the spectrum of the normal solution are very 

 striking and are typical of the changes in many other more dilute 

 solutions, a detailed account of the changes in this spectrum is given. 

 Figure 97 gives a plot of the spectra. Some attempt at indicating the 



NITRATE IN WATER. 







-35" 



-40 



-60' 



-90 



AA/ri 

 ^ M 



-120 



/TV 



. 1 



-150 



-180 



16100 



.64* ^ 



ii JL- -il 



flft I 1 



ZOIOO 



FIG. 97. 



form of the bands is made, but the changes in intensity are too great 

 to be represented on such a plot. The wave-lengths are tabulated in 

 table 118, and frequencies in table 119. At +20 only two broad bands 

 located at 0.5323 and 0.5088 were of sufficient intensity to be measur- 



