218 



FLUORESCENCE OF THE URANYL SALTS. 



In the work of Jones and Strong, 1 it was found that the absorption bands 

 persist far out into the red, only the intensity decreases with such rapidity 

 that great depths of solution were required to show them. To try this out 

 in the case of the resolved spectra of the chlorides, thick layers were built up 

 of several crystals and found out to hold. A very deep crystal was grown in 

 a glass tube ground into the bottom of an inverted bottle-neck which held the 

 solution. This crystal, which was 3 cm. thick, was never tried. 



Another investigation which was never finished was that of the char- 

 acter of the spectra of mixed crystals, of which potassium ammonium salt 

 K'NH 4 -U02'Cl4'2H 2 O was prepared as an example. 



AMMONIUM URANYL CHLORIDE. 

 (NH 4 ) 2 -U0 2 -Clr2H 2 O. 



The crystal forms of this salt are practically identical with that of the 

 potassium salt, as shown by the table of angles under that salt. Intense 

 pleochroism is noticed in this crystal when viewed through the c (001) face 

 if the crystal is about 1 mm. thick. The light vibrating parallel to the 

 b (010) edge of the face, i. e., parallel to the axis, is so little absorbed as to 

 appear white and is also least refracted. The light vibrating nearly parallel 

 to the 6 axis is strongly absorbed in the blue-violet and appears deep yellow 

 even in these crystals. The refractive indices parallel to a and nearly parallel 

 to b and c were measured on prisms cut so that light traveled parallel to the 

 c face and at right angles to it. It happens that the letters of the refractive 

 indices correspond to the axes to which they are nearest. 



The absorption is so great parallel to 6 that the value for X 500 could not 



be obtained. 



RUBIDIUM URANYL CHLORIDE. 



Rb 2 -UO 2 -CU-2H 2 O. 



This is similar to the potassium and ammonium salts; although no measure- 

 ments w'ere taken, the crystals could not be distinguished, except by knowing 



the individual crystals. 



CESIUM URANYL CHLORIDE. 



Cs 2 U0 2 Cl 4 . 



The salt was crystallized as above from a solution containing caesium chlo- 

 ride and uranyl chloride and presented a distinctly different appearance from 

 the other members of the group. This is accounted for by the composition, 

 which, according to Rimback, Wells and Boltwood, 2 is the anhydrous chlo- 

 ride instead of containing 2 molecules of water, as with the other salts. The 

 crystals were elongated rhombs of yellow color, showing less fluorescence than 

 the other salts. Under the polarizing microscope they showed a striking 



1 Jones and Strong, Carnegie Inst. Wash. Pub. No. 130, 90. 



2 Wells and Boltwood, Zeit. Anorg. Chem., 10, 181. 1895. 



