86 THE ABSORPTION SPECTRA OF SOLUTIONS. 



Ukanyl Nitrate in Nitric Acid, Uranyl Chloride in Hydrochloric Acid, 

 and Uranyl Sulphate in Scjlphuric Acid. 



Plate 67, B. The absorption of uranyl nitrate in nitric acid at 10 is rep- 

 resented in strip 1, and at about 70 in strip 2; of uranyl chloride in hydrochlo- 

 ric acid at 10 in strip 3, and at about 80 in strip 4; of uranyl sulphate in water 

 at 10 in strip 5, and at about 80 in strip 6; of uranyl sulphate in sulphuric acid 

 at 10 in strip 7, and at about 70 in strip 8. 



Every one of the uranyl nitrate bands, due to the rise in temperature, 

 seems to be shifted about 10 Angstrom units towards the red, the uranyl 

 chloride bands in hydrochloric acid being shifted about 15 Angstrom units. 



In the case of uranyl sulphate, only the uranyl bands in the region of 

 the blue-violet band were greatly shifted towards the red with rise in tem- 

 perature. The shift seemed to be considerably greater for the neutral than 

 for the acid solution. 



According to the aggregate theory we might expect that if the uranyl 

 nitric acid aggregates break down at the higher temperatures, the uranyl 

 bands would be very greatly shifted towards the red on account of less nitric 

 acid molecules affecting the uranyl vibrations. But this does not seem to be 

 the case to any very great extent, since here the shift to the red is not any 

 greater than for the other uranyl bands, and seems to be about the same for 

 each one of the bands. It may be considered that the hydrate is more simple, 

 however, and that this allows more of the nitric acid molecules to come within 

 the range of the absorbing centers, and this might in a way counteract the 

 effect of any decomposition of aggregates. Whether the effect of an increase 

 in the number of molecular collisions brings a greater number of nitric acid 

 molecules within the effective range of the absorbing centers, and has an 

 effect on the frequency, can not be decided from the spectrograms. 



The very considerable shift of each one of the uranyl chloride bands of 

 the hydrochloric acid solution towards the red with rise in temperature 

 probably indicates that there is very little decomposition of the uranyl acid 

 chloride aggregates. 



Since apparently only the e, f, g, and h uranyl sulphate bands are greatly 

 shifted towards the red, we might assume that there is a slight decomposition 

 of the uranyl sulphate aggregates, and this counteracts what we might call 

 the normal temperature shift. 



In the above strips temperature has very little effect on the uranyl bands, 

 except a shifting of their wave-lengths towards the red. 



