URANIUM SALTS. 91 



found that any uranyl compound showing a modification of the absorp- 

 tion bands shows a similar modification of the emission phosphorescent 

 bands. 



A series of spectrograms was made to test Beer's law. Exposures 

 were made under the standard conditions with 1, 0.75, 0.5, 0.33, 0.25, 0.16, 

 and 0.125 normal solutions of uranyl chloride, the corresponding depths of 

 cell being 3, 4, 6, 9, 13, 18, and 24 mm. 



There is a slight transmission band in the ultra-violet between the 

 blue-violet and ultra-violet bands. This transmission region is roughly 

 100 Angstrom units wide, and is so faint that it does not appear upon the 

 printed plates. This band obeys Beer's law. The long wave-length edge 

 of the blue-violet absorption band, however, deviates slightly from Beer's 

 law. For the 1, 0.75, 0.5, and 0.33 normal solutions the absorption is 

 slightly greater than for the 0.25 normal solution. The 0.25, 0.16, and 

 0.125 normal solutions obey Beer's law. The edge for the 1 normal solu- 

 tion is roughly 75 Angstrom units nearer the red than for the 0.25 normal 

 solution. The uranyl bands a and b are slightly stronger for the more 

 concentrated solutions. A similar run for Beer's law was made between 

 the concentrations 0.125 and 0.0156 normal. Beer's law holds in this 

 case, the absorption being complete for wave-lengths less than X 4150. 

 The uranyl bands do not appear at all. 



Uranyl, Calcium, Aluminium, and Zinc Chlorides in Water; Uranyl Chloride and 



Hydrochloric Acid in Water. 



Plate 52, A and B. were taken for aqueous solutions of uranyl chloride 

 of a constant concentration to which varying amounts of calcium chloride 

 were added. The addition of calcium chloride causes the ultra-violet, the 

 blue-violet, and the uranyl bands to widen generally. The effect upon the 

 uranyl bands is, however, very small. The effect of aluminium chloride, 

 shown in Plate 51, A and B, on the other hand, is very great. The two 

 narrow and faint bands at X 5200 appear only in the pure aqueous solution 

 of uranyl chloride. The a band in the aqueous solution is about 60 

 Angstrom units wide, and is almost as intense as the b band. The addi- 

 tion of aluminium chloride causes the band to become quite narrow, about 

 25 Angstrom units wide. A slight addition of aluminium chloride decreases 

 the intensity of the band very considerably. Further increases in the 

 amount of aluminium have very little effect. The addition of aluminium 

 chloride also causes the bands to shift to the red, the shifts in some instances 

 amounting to 25 Angstrom units. The intensity of the b and c bands is 

 very greatly increased by the addition of aluminium chloride; and by mak- 

 ing the solution about 2 normal with aluminium chloride these bands are 

 shifted about 30 Angstrom units to the red as compared with the same 

 bands for the pure uranyl chloride solution. The d, e, f, g, and h bands 

 are also increased in intensity, but are only very slightly shifted to the red. 

 The d and e bands are widened so that they form practically a single band. 



In order to bring out the similarity of the action of aluminium chloride 

 on uranyl and on uranous chlorides, the absorption spectra of a 0.2 normal 

 solution of uranyl chloride in water (Plate 49, A), and of a 0.2 normal 



