FROZEN SOLUTIONS. 203 



will the spectra of such solutions. This appeared to be somewhat 

 independent of the rate of cooling ; thus, it was discovered that a solu- 

 tion might yield a spectrum consisting of a set of broad-banded 

 doublets at one time and a narrower set of doublets differently spaced 

 at other times. The three spectra shown at the bottom of figure 96 

 illustrate this phenomenon. The first two spectra, although entirely 

 "different, were produced from a solution of 1 part normal aqueous 

 solution with 10 parts nitric acid. The first was obtained after very 

 slow cooling, the second after moderately slow cooling to liquid air. 

 The second spectrum is identical with the third, obtained by slowly 

 cooling a solution of 1 c.c. of normal solution to 3.5 c.c. of nitric acid. 

 Such experiments lead to the view that the luminescence spectrum is 

 determined by the particular hydrate which is formed on freezing. 



The frequency interval of an acid or aqueous solution was always 

 constant. The change in interval through a wide range of dilutions 

 was slight. The largest interval was of 87 + , the smallest of 84+ 

 units. 



NITRATE IN WATER & ETHYL ALCOHOL. Kl 



-90 



-120 



-150" 





^ . 



5-5 MITRATE IN ALCOHOL;ETHYL. 

 -90' 



-120 



-ISO* 



-IBS' 



isloo | leloo | 2o|oo 



.eolx* selx* .szL 



J- NITRATE IN ALCOHOL: METHYL. 



I A 



-120 



X . 



-135' 





-185 



A 



yiv 



ie|oo _ | _ 20)00 



FIG. 106. 



