URANIUM SALTS. 99 



At 82 the ultra-violet band extends to X 3700, and the blue-violet 

 band from X 3950 to X 4600. At this temperature only the b band appears, 

 a being very weak and c completely merged into the blue-violet absorption 

 band. The b band is located at X 4755. 



A spectrogram (Plate 61, B) was made of a 0.0156 nomal aqueous 

 solution of uranyl chloride 196 mm. deep. Exposures were made to the 

 Nernst glower for 30 seconds (current 0.8 ampere and slit-width 0.20 mm.). 

 No exposures were made to the spark except for comparison spectra. 

 Starting with the numbered scale, the temperatures were 6, 18, 29, 44, 

 59, 71, and 79. 



For this concentration there is a very slight temperature effect. There 

 is a very faint transmission band between the ultra-violet and blue-violet 

 bands. This is extremely faint and is practically unaffected by tempera- 

 ture. The blue-vio et band widened slightly with rise in temperature. 

 The uranyl bands in the concentrated solution were much stronger and 

 wider than in the dilute solution. 



Absorption Spectrum of Anhydrous Uranyl Chloride. 



The absorption spectrum of the anhydrous chloride was photographed 

 in the same way as that of the anhydrous nitrate. The bands differ con- 

 siderably from the bands of the aqueous solution, and one cannot tell very 

 well whether they are identical with the corresponding a, b, c, etc., bands 

 of the solution or not. Their wave-lengths are approximately as follows: 

 XX 4950 (narrow), 4860, 4765, 4700, 4615, 4540, 4460, 4320, 4290, 4160, 4050, 

 and 3940. 



ABSORPTION SPECTRUM OF URANYL NITRATE UNDER DIFFERENT CONDITIONS. 



Uranyl Nitrate in Aqueous Solution. 



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

 uranyl salts. With a depth of solution of 3 mm. its absorption spectrum 

 (Plate 62, A, B) was investigated between concentrations of 1.5 normal 

 and 0.0234 normal. For the 1.5 normal solution the absorption consists of 

 a band in the blue-violet and absorption throughout the ultra-violet portion 

 of the spectrum. As the concentration decreases 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 concentration of 0.5 normal, and there is almost complete trans- 

 mission 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 ab- 

 sorption band these bands are relatively quite clear. As the absorption 

 edge recedes from the uranyl bands, the general transmission is so great as 

 to obscure them almost completely. 



A, Plate 63, represents the absorption spectra of an aqueous solution 

 of uranyl nitrate of different depths of layer. The narrow and rather weak 

 bands shown here are the uranyl bands. Twelve of these bands have been 

 photographed. Starting with the band of longest wave-length they will be 

 designated by the letters a, b, c, d, etc. On account of the irregularity of 



