URANIUM SALTS. 123 



Strip 1 shows complete ultra-violet absorption up to about X 3300. 

 Two absorption bands XX 4200, 4400 almost merge into each other. Of 

 these the one with shorter wave-length (X 4270) is considerably stronger 

 than the other (X 4370). A strong band appears at X 4980, about 30 Ang- 

 strom units wide. This is limited by a wide region of general absorption, 

 which widens out very rapidly towards the vio'et with increasing depth of 

 cell. This is most likely due to the presence of diffuse bands in this region. 

 The diffuse band at X 5500 widens symmetrically w th increasing depth of 

 cell. There are two very strong bands which for 2 mm. depth of cell are 

 situated at X 6430 to X 6620 and X 6720 to X 6770. This region of ab- 

 sorption is a very characteristic one for uranous chloride in water. Other 

 diffuse bands appear at X 3910, X 4030, X 4600, and X 6340. 



Uranous and Aluminium Chlorides in Water. 



Uranyl chloride was reduced in the presence of an aluminium chloride 

 solution of about 2.4 normal concentration. The concentration of uranous 

 chloride was 0.17 normal. Plate 84, B, represents the absorption spectrum, 

 the depths of cell being 1.2, 2, 4, 8, 16, and 32 mm. 



The resulting spectrum is very much like that of the pure aqueous 

 solution. The ultra-violet absorption is much greater; the absorption 

 extending to about X 3800. The presence of aluminium brings out several 

 bands in the blue-violet region which we shall continue to designate as the 

 uranyl bands. These bands have the same wave-lengths as the correspond- 

 ing wave-lengths of the uranyl bands of a solution of uranyl and alumin- 

 ium chlorides in water. 



The band at X 5000 is much more diffuse than the corresponding band 

 for water. The band at X 5570 widens symmetrically with increasing depth 

 of cell. Besides these bands there are two bands at X 6550 to X 6640 and 

 X 6750 to X 6800. The gen ral effect of the aluminium chloride is to bring 

 out the uranyl bands; to increase the ultra-violet absorption; to make the 

 band X 5000 and others slightly more diffuse, and to cause the uranous 

 bands to shift towards the red, about 20 or 30 Angstrom units. 



The concentration of uranium in a solution necessary to bring out the 

 uranyl bands either in the uranyl or uranous condition is about the same. 



Spectrogram, Plate 98, A, shows the effect of the presence of aluminium 

 chloride and hydrochloric acid upon the uranous bands. Strip 1 represents 

 the absorption of a 3 mm. 0.17 normal solution of uranous chloride in water; 

 strip 2 the same to which a 3.04 normal solution of aluminium chloride 

 had been added, so as to make the depth of cell 4 mm.; strip 3 a depth 

 of cell of 6 mm.; strip 4 represents the same as strip 1; strip 5 is the 

 absorption of the solution of strip 4, to which sufficient hydrochloric acid 

 had been added to make a depth of cell of 16 mm. Both aluminium 

 chloride and hydrochloric acid cause the ultra-violet absorption to increase 

 very much. Aluminium chloride has much the same effect as hydrochloric 

 acid, although not so great. It does not change the water-bands X 6400 

 and X 6655 as does hydrochloric acid. Strip 3 gives bands at the follow- 

 ing positions: g, X 4140;/, X 4280 (strong); e, X 4400 (e and /almost merge 

 into each other); d, X 4490; c, X 4620; b, X 4780, X 4990, X 5550, X 6460 to 

 X 6660, /6780. 



