CHEMISTRY OF FLUORESCING URANYL SALTS. 221 



CAESIUM URANYL SULPHATE. 

 Cs 2 UO 2 (SO 4 ) 2 3H 2 O. 



This salt is so insoluble that no crystals could be produced. The Crag wall 

 product recrystallized showed on the microscope-slide square plates about 

 10 jit in length, which showed a negative uniaxial figure. This salt, according 

 to de Coninck, 1 has the same composition which he finds for the potassium 



salt, that is, 3H 2 0. 



AMMONIUM URANYL SULPHATE. 



(NH 4 ) 2 U0 2 (S0 4 ) 2 2H 2 O. 



This salt was not recrystallized, but showed similar characteristics to the 

 potassium salt. When recrystallized it gave bundles of needles, the vibra- 

 tions across which were most absorbed and most refracted. Rimbach de- 

 scribes the salt as having 2 molecules of water. The crystals were found to be 

 monoclinic by de la Provostaye. 2 



SODIUM URANYL SULPHATE. 

 Na 2 UO 2 (SO 4 ) 2 3H 2 O. 



This salt is described by de Coninck as having 3 molecules of water, which 

 he finds also in the potassium salt. This salt as prepared by Cragwall was 

 not recrystallized, but showed under the microscope one optical axis and the 

 acute bisectrix with positive double refraction. It is, therefore, presumably 

 triclinic, as the acute bisectrix was off normal in both directions. 



THALLOUS URANYL SULPHATE. 

 T1 2 UO 2 (SO 4 ) 2 3H 2 O. 



This salt was prepared by Cragwall from weighed amounts of the two salts 

 according to Kohn, 3 who found the salt to be of the above composition with 

 probably 3H 2 0. The crystal description by Himmelbauer in the same 

 article gives the system as rhombic, the symmetry from etch figures pyramidal. 

 The forms are the three pinacoids with pyramid faces at the corners which 

 were too small to measure. He observed through (100) in converged polarized 

 light the plane of the axes for red and blue, at right angles the plane of the 

 blue being that of the a and c axes; for green nearly uniaxial; for red light 

 a is the acute bisectrix, the pleochroism on (100) distinct, parallel to c, deep 

 yellow; parallel b yellowish white, but no noticeable pleochroism on (010). 

 Crystals up to 3 mm. in diameter and 1 mm. thick, produced by slow cooling 

 of the Cragwall salt, showed the axial figure, but it could not be surely seen 

 to agree with the description, due to the intense absorption in the blue and 

 green. The figure might be explained by anomalous dispersion due to the 

 absorption band. 



PHOSPHATES. 



Uranyl phosphate (HUO 2 PO 4 .3|H 2 0), which precipitates from uranyl solu- 

 tions on adding phosphates, possesses no fluorescence. If it is dissolved 

 in an excess of acid it gives a glass or sirup with a brilliant fluorescence which 

 can not be resolved beyond the bands. The sodium double salt was made 

 by adding sodium phosphate to produce H 2 Na2C0 2 (P0 4 ) 2 to the uranyl 

 phosphate with an excess of water, which on standing and evaporating gave 



1 de Coninck, Bull. Acad. Roy. Belg., 1905, 94. 



2 de la Provostaye, Ann. Chim. Phys. (3), 5, 51. 1842. 



3 Kohn, Z. Anorg. Chem., 59, 111. 1908. 



