72 THE ABSORPTION SPECTRA OF SOLUTIONS. 



B, plate 16, shows a spectrophotograph of the changes^produced in a 

 nitric acid solution of uranyl chloride to which increasing amounts of a concen- 

 trated solution of aluminium chloride in water are added. The spectrogram 

 shows the very great increase in the amount of the ultra-violet absorption 

 on the addition of the aluminium chloride. The blue-violet band does not 

 appear at all. The uranyl bands are shifted slightly towards the red, and 

 apparently change but slightly in intensity. The change from the first to[the 

 second strip is brought about by the addition of three drops of the aluminium 

 chloride solution. 



Plate 17 is to show the different effect produced by adding an acidjmd 

 a neutral salt. .4 represents the absorption of uranyl nitrate in nitric acid 

 to which hydrochloric acid is added, and this plate can be compared directly 

 with B, plate 16. B, plate 17, on the other hand, shows the effect of the 

 addition of an aqueous solution of aluminium chloride to an aqueous solution 

 of uranyl nitrate. 



A, plate 17, shows the increase in the ultra-violet absorption. The great 

 increase is in the intensity of the middle uranyl bands, whereas in the case 

 of the first strip the intensity of the various uranyl bands was much more 

 evenly distributed. A very small amount of hydrochloric acid produced a 

 very great change in the uranyl bands. The addition of aluminium chloride 

 produces a much more gradual change in the position and character of the 

 uranyl bands. It produces a much greater change in the ultra-violet absorp- 

 tion, causing the uranyl bands to shift towards the red and to increase very 

 great!}- in intensity. 



A, plate 22, shows the effect of the addition of calcium nitrate to an 

 aqueous solution of uranyl nitrate. 



