204 JONES-STRONG— THE ABSORPTION SPECTRA [April 24, 



wave-length are slightly wider. The i band is considerably weaker 

 than its neighboring bands. 



(b) Absorption Spectrum of Uranyl Nitrate Crystals. 

 In the aqueous solution there is no sign that the bands can be 

 broken up. In the crystal spectrum 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 A 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 a. u. wide, and 

 the e band is about 70 Angstrom units wide and appears double. The 

 / band is the most intense and is about 40 A. u. wide. The bands 

 g, h, i and ; keep decreasing in intensity respectively. The above 

 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 ex- 

 posure and various other things. The above spectrogram showed 

 many details, however, that other spectrograms did not. It will 

 thus be seen that the a, b, c, d, j and k bands of the solution agree 

 fairly well with those of the crystal, and that the crystal bands 

 /, g, h and i are shifted towards the red with reference to the 

 bands in the aqueous solution. 



(c) Effect of Dilution upon the Uranyl Bands. 

 The effect of dilution on the position and intensity of the blue- 

 violet, the ultra-violet and the uranyl bands of the acetate, nitrate 

 and sulphate of uranyl in water was tried. The absorption spectra 

 of solutions of about i normal and 3 mm. depth of cell was photo- 

 graphed along by the side of the absorption spectra of the same 

 salts of 0.008 normal concentration and 380 mm. depth of layer. 

 The absorption consisted of the blue-violet band, the ultra-violet 

 band and the a, b, c, i, j and k bands. Between the blue-violet and 

 ultra-violet bands there was the transmission band containing i, j 

 and k. For each of the three salts this transmission band was 

 much weaker for the dilute solution, whereas in the cases of the 

 sulphate and nitrate the long wave-length transmission edge of the 

 blue-violet band was stronger for the more dilute solution. The 

 opposite was true of the acetate solution. In the dilute solution of 



