1909.] OF VARIOUS SALTS IN SOLUTION. 231 



ably show as finer bands. The band at A 6540 is much more 

 diffuse on the red than on the violet side ; this possibly being due to 

 a component that is not separated at this temperature. Other bands 

 are located at AA5365, 5380, 5425, 5445, 5505, 6410, 6440, 6495 and 

 6690. 



The general effect of rise in temperature here is to cause the 

 lines to become slightly fuzzier and to show more of a " washed 

 out" appearance. No shift due to rise in temperature was noticed. 



Throughout all the previous work the wave-lengths were read 

 directly from a scale. This scale was made so as to give the wave- 

 lengths in Angstrom units directly. It was found in the measure- 

 ments that the Seed films did not correspond to the Wratten and 

 Wainwright films, when the same spark spectra on the two kinds 

 of films were placed beside one another. This was probably due 

 to different shrinkage of the two kinds of films on fixing, washing 

 and drying. For this reason the wave-length measurements are not 

 intended to be absolutely correct but only relatively so. All the 

 temperature work was done with Wratten and Wainwright films. The 

 relative measurements of fine bands for any spectrogram are prob- 

 ably correct to within a few Angstrom units. 



X. Summary. 



The absorption spectra of the uranyl salts contain a series of 

 bands in the blue and violet. Twelve of these bands can usually 

 be detected for each salt. Starting from the blue end of the series 

 the bands are designated by the letters a, b, c, etc. These bands 

 are usually diffuse and from 30 to 50 Angstrom units wide. 



The uranyl bands of uranyl nitrate in water are all farther to the 

 violet than the uranyl bands of any other salt investigated, or of 

 uranyl nitrate in other solvents. 



The uranyl absorption bands of crystals of uranyl nitrate agree 

 with the absorption bands of an aqueous solution of the nitrate, 

 with the exception of the /, g, h and i bands; these latter being 

 shifted to the red in the crystal. 



Dilution within the ranges studied does not affect the position 

 of the uranyl bands. Theoretically, all the uranyl salts in water 



