IK) A STUDY OF THE ABSORPTION SPECTRA. 



strom units wide and appears sometimes to be double; d, -14380 (70 Ang- 

 strom units); e, X 4240 (70 Angstrom units wide); /, X 4100; g, X 3980; 

 h, X 3870; i, X 3770; /, X 3660. 



Ukanyl Acetate in Water. 



Uranyl acetate crystallizes from an aqueous solution at ordinary tem- 

 peratures as UO^CHgCOO^HjjO. The aqueous solution of this salt is 

 very similar to that of the uranyl salts previously described, showing the 

 blue-violet and ultra-violet bands and also the characteristic uranyl bands. 

 This salt in solution is much more highly colored for the same concentra- 

 tion than the nitrate or bromide. 



Plate 74, B, represents the absorption of a series of solutions where 

 the concentration was kept constant and the depth of layer varied. The 

 usual procedure was to keep the concentration constant and vary the depth 

 of cell. For salts obeying Beer's law this would give the same absorption 

 as keeping the depth of cell constant and varying the concentration, so that 

 in our spectrograms of a salt where Beer's law holds no difference is made 

 between these two cases. Where Beer's law is deviated from, the two cases 

 will not be identical. For the case under consideration the concentration 

 was 0.031 normal and the depths of cell, starting with the strip nearest the 

 numbered scale, were 24, 18, 12, 9, 6, 4, and 3 mm. The length of exposure 

 to the Nernst glower with 0.08 ampere and a slit-width of 0.08 mm. was 

 1 minute. 



The blue-violet band has the boundaries XX 4500 and 4050 for a 24 mm. 

 cell, and XX 4400 and 4100 for a depth of 18 mm., the middle of the band 

 thus coming at about X 4250. The long wave-length edges of the ultra- 

 violet band are XX 3750, 3700, 3680, 3660, 3630, 3600, and 3580 for depths 

 of cell of 24, 18, 12, 9, 6, 4, and 3 mm., respectively. 



A photograph was made to bring out the small uranyl bands. An 

 exposure was first made for 1 minute (0.08 ampere and 0.08 mm. slit) in 

 the yellow end of the spectrum. This solution was 15 mm. deep in every 

 case. The screen was interposed so as to cut off all light of greater wave- 

 length than X 4450. A long exposure to the Nernst filament about 5 

 minutes was then made. Another screen was then interposed which cut 

 out all light of wave-length greater than X 2800, and an exposure made to 

 the spark. During these three exposures nothing was moved except the 

 screen, and thus the question of any mechanical moving of the photographic 

 film was eliminated. From these two plates the positions of 9 uranyl bands 

 were measured. These were as follows: a, 4910 (?) ; b, 4740; c, 4595; d, 

 4455(?); e, 4310;/, 4160; g, 4070; h, 3970; i, 3865. 



It will be seen that these bands are all nearer the red than the bands 

 of uranyl nitrate in water. 



Deussen found the following values: a, 4875; b, 4730; c, 4575; d, 4420; 

 e, 4310; /, 4180; g, 4060; h, 3950; i, 3860; /, 3770. These are in satisfactory 

 agreement with the values given above. 



The spectrogram, Plate 74, A, represents the change in absorption of 

 uranyl acetate with concentration when the amount of salt in the path of 

 the light beam is kept constant. The exposure was 1 minute to the Nernst 



