1909.] OF VARIOUS SALTS IN SOLUTION. 211 



{b) Absorption Spectrum of Anhydrous Uranyl Chloride. 



The absorption spectrum of the anhydrous uranyl chloride was 

 photographed in the same way as that of the anhydrous nitrate. 

 The bands differ considerably from the bands of the aqueous solu- 

 tion, and one cannot tell very well whether they are identical with 

 the corresponding a, b, c, etc., bands of the solution or not. Their 

 wave-lengths are approximately as follows: AA4950 (narrow), 4860, 

 4765, 4700, 4615, 4540, 4460, 4320, 4290, 4160, 4050 and 3940. 



(c) The Characteristic Bands of Uranyl Chloride. 

 In addition to the bands already described, uranyl chloride has 

 several remarkably fine bands in the green. These bands are not 

 more than 5 Angstrom units wide and were first seen on spectro- 

 grams taken upon Whatten and Wainwright red sensitive films, 

 They appear only for aqueous solutions, and the addition of cal- 

 cium chloride or aluminium chloride causes them to disappear. 

 They do not appear in alcoholic solutions. Aqueous solutions of 

 uranyl sulphate show them very faintly. The wave-lengths are 

 approximately as follows : 



AA,5i85, 5200, 6000, 6020, 6040 and 6070. 



These bands have never hitherto been noticed as absorption 

 bands. H. Becquerel' gives quite a full set of measurements of the 

 phosphorescent bands of various uranyl salts at room temperature 

 and at the temperature of liquid air. Among the bands given for 

 the double chloride of uranyl and potassium at room temperature 

 are AA6070 to 6040, and AA5220 to 5193. Whether these corre- 

 spond to the above absorption bands is quite difficult to say. Fur- 

 ther work is being done in this direction. 



{d) Uranyl, Calcium and Aluminium Chlorides in Water. 

 Spectograms were taken of aqueous solutions of a constant con- 

 centration of uranyl chloride to which varying amounts of cilcium 



'C. R., t. loi, p. 1252, 1885; pp. 459 and 621, 1907. 



