URANIUM SALTS. 



101 



In the original film from which A, Plate 63, was made all of these bands 

 except d could be very distinctly seen. The bands of longer wave-length 

 are slightly wider. The i band is considerably weaker than its neighboring 

 bands. 



Spectrograms (Plate 64, A and B) were made by exposing to the 

 Nernst filament for 1 minute at 0.8 ampere, the slit-width being 0.08 mm. 

 The spark was run about 3 minutes. In A the concentrations were 1.5, 

 1.125, 0.75, 0.5, 0.375, 0.25, and 0.1875 normal; in B, 0.1875, 0.14, 0.094, 

 0.0625, 0.047, 0.0312, and 0.0234 normal, starting in each case with the 

 strip next to the spark-spectrum. The corresponding depths of cell were 

 3, 4, 6, 9, 12, 18, and 24 mm. respectively. In the case of the more concen- 

 trated solutions Beer's law was not found to hold. In A there appear 

 the two wide absorption bands. The large wave-length limit of the ultra- 

 violet band is independent of the concentration when the amount of salt 

 is kept constant, and is located at about X 3520. The blue-violet band on 

 its short wave-length side also obeys Beer's law and ends at X 3860. The 

 long wave-length edge, however, is pushed towards the red as the concen- 

 tration is increased; or, in other words, the absorption is greater for a 

 given amount of salt in concentrated solutions than it is in dilute solutions. 

 The positions of this edge for various concentrations are X 4100 for 0.1875, 

 0.25, 0.375, and 0.5 normal; X 4150 for 0.75 normal; X 4300 for 1.125 

 normal; and X 4340 for 1.5 normal. For B Beer's law holds and only the 

 ultra-violet absorption band appears; its long wave-length side being at 

 X 3350. The intensities of the small bands are independent of concentra- 

 tion as far as one can tell from the spectrograms. 



Absorption Spectrum of Uranyl Nitrate Crystals. 



For the aqueous solution there is no sign that the bands can be broken 

 up. In the spectrum of the crystal this is not the case. The a band is 

 narrow. The b band is also very narrow, about 15 Angstrom units wide. 

 A very faint band appears about ^4650. The c band, on the other hand, 

 is very wide, about 70 Angstrom units, and is probably double. The d 

 band is about 50 Angstrom units wide, and the e band is about 70 

 Angstrom units wide and appears double. The / band is the most intense 

 and is about 40 Angstrom units wide. The bands g, h, i, and / keep de- 

 creasing in intensity respectively. The description is of a spectrogram 

 taken of a crystal in Canada balsam, and of course the width of the bands 

 varies with the time of exposure and various other things, but many details 



