I909.] OF VARIOUS SALTS IN SOLUTION. 201 



small. Of the potassium salts above described, only potassium 

 chromate between 2 normal and 0.25 normal showed any consider- 

 able deviation from Beer's law, and in this case the absorption of 

 the concentrated solution was greater than would be expected if 



o 



Beer's law held by about 40 Angstrom units. 



The present method is a very good qualitative test of Beer's law, 

 and gives the results for each wave-length, whereas most photo- 

 metric methods only give integrated results over a more or less wide 

 region of wave-lengths. 



III. Absorption Spectrum of Uranyl Nitrate under Different 



Conditions. 

 There are two groups of uranium salts, the uranyl salts con- 

 tainiijg the UO, group, and the uranous salts. The uranyl salts in 

 solution are yellow and usually crystallize from aqueous solu- 

 tions with a certain amount of water of crystallization ; for ex- 

 ample, at ordinary temperatures uranyl sulphate crystals have the 

 composition U02(S04)23H20. The uranous salts are intensely 

 green and are very unstable, oxidizing very easily to the uranyl 

 condition. Uranous sulphate crystals have the composition 

 U(SOj29HA 



(a) Uranyl Nitrate in Aqueous Solution. 



The spectrum of uranyl nitrate in water is a typical example of 

 the uranyl salts. Using a depth of solution of 3 mm. its absorp- 

 tion spectra was investigated between concentrations of 1.5 normal 

 to 0.0234 normal. For the 1.5 normal solution the absorption con- 

 sists of a band in the blue-violet and absorption throughout the 

 ultra-violet portion of the spectrum. As the concentration de- 

 creases the blue-violet band fills up with transmission, and the 

 , ultra-violet absorption is pushed farther and farther out into the 

 ultra-violet. The blue-violet band is practically gone at a concen- 

 tration of 0.5 normal, and there is almost complete transmission 

 throughout the ultra-violet for concentrations less than 0.02 normal. 



During these changes in concentration a large number of bands 

 about 50 Angstrom units wide make their appearance. Near the 

 edge of an absorption band these bands are relatively quite clear. 



