EFFECT OF DILUTION ON ABSORPTION OF LIGHT. 25 



This spectrogram shows complete absorption in the violet to about X4500, 

 with a well-defined band near X4700. The latter widens uniformly with 

 increase in concentration. It is scarcely visible in strip 1, but becomes about 

 75 a.u. wide in the top strip. The most concentrated solution (strip 6) 

 shows decidedly more absorption towards the red. The change in both of 

 these bands is decidedly the most pronounced between strips 5 and 6, i. e., 

 where the percentage change in dilution is greatest. 



B contains the absorption spectra of a series of solutions whose respective 

 concentrations are just half of those in A, the corresponding depths of 

 absorbing layer being the same as in A. 



There is faint transmission near X3800, with complete absorption of all of 

 the wave-lengths from this region to X4400. None of the bands shows any 

 change with dilution. In a word, Beer's law seems to hold perfectly for 

 these dilutions. 



URANYL NITRATE IN WATER. (See Plate 22.) 



The concentrations of A, beginning with the strip farthest removed from 

 the numbered scale, were 1.55, 0.775, 0.387, 0.269, 0.0155, and 0.0031 nor- 

 mal, the corresponding depths of cell being 0.5, 1, 2, 3, 50, and 250 cm. 



In B, the concentrations were just half of those in A, the same depths of 

 cell being employed. The negative of A shows the bands with special 

 clearness. 



In strip 1 there is complete absorption of the violet to X4500. This 

 gradually recedes towards the red, with increase in concentration amount- 

 ing to as much as 100 a.u. The X4700 band widens about 20 a.u. There is 

 a sharp band, X4878, which widens slightly with increase in concentration. 



B shows faint transmission around X3750, with broad, intense absorption 

 to X4350. Absorption bands, which are unchanged by change in dilution, 

 appear at X4550, X4700, and X4850. The only change in the bands on this 

 plate is a slight encroachment on the red of the broad violet absorption in 

 strip 6. 



The results recorded on this plate are in complete accord with those of 

 plates 20 and 21, which are the corresponding absorptions of uranyl chloride 

 and uranyl bromide. A , in all three of these plates, represents the most con- 

 centrated solutions, while B represents half the concentrations in A . Most 

 of the bands in A show well-marked widening with increase in the concen- 

 tration, while in B the change is scarcely detectable. 



