208 JONES-STRONG— THE ABSORPTION SPECTRA [April 24, 



which no explanation so far has been suggested. In the work on 

 the effect of rise of temperature on the absorption spectrum it 

 was found that the uranyl nitrate bands did not shift to the red. 

 On the other hand, the uranyl .sulphate and uranyl chloride bands 

 were shifted to the red under the same conditions. (In these cases 

 aqueous solutions were investigated.) If the uranyl nitrate bands 

 owe their position to a large amount of hydration it would be ex- 

 pected that with rise in temperature they would be shifted towards 

 the red more than the bands of the sulphate and chloride. Another 

 difficulty is that of the effect of dilution. The greater the dilution 

 the greater the dissociation, and, therefore, according to the theory 

 of Arrhenius for very dilute solutions the UO2 group should exist 

 in the ionic condition and the absorption spectrum of all the salts 

 should be the same, i. e., the uranyl bands should then occupy the 

 same positions independent of the kind of salt. No effect of this 

 kind is to be noticed, as was shown above under the division de- 

 scribing the effect of dilution. It is intended to use much more 

 dilute solutions in the future. 



IV. The Absorption of Uranyl Bromide, Uranyl Acetate and 

 Uranyl Sulphate. 



(a) Absorption Spectrum of Uranyl Bromide in Water. 

 The absorption spectrum of uranyl bromide in water was 

 mapped and found to be very similar to that of the nitrate. The 

 ultra-violet, blue-violet and uranyl bands appear and are affected in 

 the same manner as the same bands of the nitrate. Beer's law was 

 found to hold. The uranyl bands were found to be much wider 

 and more diffuse than in the case of the aqueous solution of the 

 nitrate. The following are their approximate positions : 



a b c d e f 



4880 4720 4560 4450 4280 4160 



(b) Uranyl Acetate in Water, Beer's Laiv. 



A spectogram was made to test whether Beer's law holds for 



an aqueous solution of uranyl acetate between the concentrations 



0.25 normal and 0.031 normal. The spectrogram showed that there 



was a very great deviation from the law, and in the opposite direc- 



