24 ABSORPTION SPECTRA OF SOLUTIONS. 



PRASEODYMIUM NITRATE IN WATER, (See Plate 19.) 



The concentrations of the solutions used in A, beginning with the strip 

 farthest removed from the numbered scale, were 2.6, 0.026, and 0.0052 nor- 

 mal; the corresponding depths of cell being 0.5, 50, and 250 cm. 



The concentrations in B were just half of those in A, and those in C were 

 half of those in B. None of the absorption bands shows airy change with 

 dilution in either B or C. In A there is a slight change in the X4450 and 

 X4650 bands. Each of these bands widens about 20 a.u. with concentration 

 over the range of concentration studied. 



With praseodymium nitrate, as with the chloride previously discussed, 

 there is only very slight change in the absorption with change in dilution. 



URANYL CHLORIDE IN WATER. (See Plate 20.) 



The concentrations of solutions used, beginning with the strip farthest 

 removed from the numbered scale, were 1.363, 0.682, 0.341, 0.227, 0.01363, 

 and 0.00272 normal; the corresponding depths of cell being 0.5, 1, 2, 3, 50, 

 and 250 cm. In making this spectrogram, no additional exposure was made 

 in the ultra-violet. The last four strips, one being nearest the numbered 

 scale, were each exposed 30 seconds to the Nernst glower. The first two 

 strips, on account of the length of cell used, had to be exposed a much longer 

 time. In this, as in all other cases, the length of exposure was governed 

 solely by the time required to give a clear print on the plate. 



There is complete absorption of all the light having wave-lengths shorter 

 than X4500, well-defined bands with rather hazy edges appearing near X4700 

 and X4900. There is also rather diffuse absorption near X5500 and X6100. 

 The two last-named bands are too ill-defined for detailed discussion. 



The X4700 band shows marked widening with increase in concentration, 

 the change being greater towards the red end of the spectrum. The entire 

 band is about 50 a.u. The X4900 band shades off rapidly towards the red 

 end of the spectrum, but not so much as the band X4700. The greatest 

 change is between strips 5 and 6, i. c, where the change in dilution is greatest. 



The concentrations in B were just half of those in A. Starting with the 

 strip away from the scale, they were 0.685, 0.340, 0.170, 0.1135, 0.00685, and 

 0.00136 normal. The depths of the cell were the same as in A, 0.5, 1, 2, 3, 

 50, and 250 cm. 



The changes produced by dilution, as shown in B, are much less marked 

 than in A . Indeed, this would be expected, since the concentrations of the 

 solutions were less. There is, however, a gradual widening of both X4600 

 and X4700 bands as the solution becomes more concentrated. The greatest 

 change is in strips 5 and 6. 



URANYL BROMIDE IN WATER. (See Plate 21.) 



The concentrations of the solutions used in making A, beginning with the 

 strip farthest removed from the numbered scale, were 1.365, 0.682, 0.341, 

 0.227, 0.01365, and 0.0027 normal, the corresponding depths of layer being 

 0.5, 1, 2, 3, 50, and 250 cm. 



