URANIUM SALTS. 109 



The rise in temperature from 5 to 84 caused an encroachment of the 

 ultra-violet band into the regions of greater wave-length. The blue-violet 

 band increased in width, especially towards the red, as the temperature was 

 raised. The uranyl bands themselves changed very slightly in intensity 

 with rise in temperature. 



At 5 the ultra-violet was absorbed to X 3500. The blue-violet band 

 extended from X 3900 to X 4400. The uranyl bands a, b, and c appeared at 

 XX 4570, 4730, and 4910. 



At 84 the ultra-violet band extended to X 3600, the blue-violet 

 band from X 3850 to X 4550. The bands a, b, and c have become con- 

 siderably more diffuse. Their positions are XX 4590, 4745, and 4925, 

 approximately. 



A much more dilute solution (0.0156 normal) of uranyl sulphate 

 (Plate 73, B), containing approximately the same amount of salt as the 

 concentrated solution, was used. The length of cell in this case was 196 

 mm. The exposure was for 30 seconds to the Nernst glower (current 0.8 

 ampere, slit-width 0.20 mm.). The time of exposure to the spark was 4 

 minutes. Starting with the strip next to the comparison spectrum, the 

 temperatures were 6, 19, 36, 51, 67, and 81. 



At 6 the ultra-violet band extends to X 3500 and the blue-violet 

 band from X 3950 to X 4450. The positions of the a, b, and c bands are 

 XX 4565, 4720, and 4895. At 81 the ultra-violet absorption extended to 

 X 3600 and the blue-violet band from X 3900 to X 4500. The a and b bands 

 were located at XX 4735 and 4915. The effect of concentration on the 

 temperature coefficient seems to be very small. In both concentrations, 

 as the temperature was raised there was a slight shift of the uranyl bands 

 to the red. 



Several spectrograms were made in order to get the absorption spectra 

 of the dry (anhydrous) uranyl sulphate. The bands were extremely faint, 

 however, and no reliable measurements of their position could be made. 



Uranyl Sulphate Mixed with Concentrated Sulphuric Acid. 



Several spectrograms were taken to find whether the addition of very 

 concentrated sulphuric acid to an aqueous solution of uranyl sulphate pro- 

 duced any effect. A normal solution was used a spectrogram being taken of 

 this solution. Very concentrated sulphuric acid was added until the length 

 of the layer was 57.6 mm.; the concentration being then 0.052 normal. 

 In both spectrograms the position of the long wave-length side of the blue- 

 violet band remained the same. The bands a and b appear in both cases, 

 and c rather faintly. In the aqueous solution b is about five times stronger 

 than a. In the sulphuric acid mixture, however, a increases in intensity; 

 i.e., its absorption becomes greater; whereas b becomes considerably nar- 

 rower, so that a and b have about the same intensity. The uranyl sulphate 

 bands in the sulphuric acid solution resemble very closely the same bands 

 for uranyl nitrate crystals. 



In very strong sulphuric acid the bands of uranyl sulphate have 

 the following wave-lengths: a, X 4930, about 30 Angstrom units wide; 

 b, X 4745, almost identical in character with a; c, X 4550, about 80 Ang- 



