220 



FLUORESCENCE OF THE URANYL SALTS. 



These salts were all prepared by crystallization from water of the calculated 

 quantities of the two single salts. Rimbach 1 describes the potassium ammo- 

 nium and rubidium salts as having each 2 molecules of water of crystallization. 

 On the other hand, de Coninck 2 describes the sodium potassium and Cfiesium 

 salts as having 3 molecules of water, while the ammonium commonly has 2, 

 but can be made by special conditions with 3 molecules. 



POTASSIUM URANTL SULPHATE. 

 K 2 UO 2 (S0 4 )22H 2 O. 



This salt separates readily on cooling a hot saturated solution of the two 

 salts in equimolecular proportion. This, according to Rimbach, gives the 

 dihydrate, according to de Coninck 3 the trihydrate. The salt prepared in this 

 way is a fine crystalline powder, larger masses being clusters of crystals. A 

 good crystal was discovered in an old solution of known strength. They 

 were then obtained by supersaturating 0.1 to 0.5 gram of salt in 50 to 200 c.c. 

 of solution, seeding, and allowing the tightly stoppered solution to stand from 

 3 to 6 months, especially in the fall, when the room temperature gradually 

 decreases. The crystals tend to form rosettes, clusters of crystals arising 

 from the middle of the basal pinacoid. The smaller crystals are tabular on 

 the base; the larger ones have large prism faces made up really of repeated 

 pyramids. These are capped by the unit pyramid with brachydome and 

 basal pinacoid. 



System rhombic; axial ratio a : b : c = 0.5889: 1: 0.6253. 



cole. 



6:m = 010:110 = 32 1' 

 c: n = 001:101=43 18' 



c: = 001:201= 



c: fc = 001:011=3030' 



c: 1 = 001: 021= 



c: 3 = 001:112 = 29 4' 



obs. 

 32 13' 

 43 0' 

 62 3' 

 30 19' 

 49 20' 

 30 0' 



calc. 



c: p = 001:lll=48 2' 

 c: r = 001:332=59 3' 

 c: s = 001:221 =65 47' 

 c: t =001:331 =73 18' 

 c:w = 001:441 = 7720' 



obs. 



48 6' 

 59 30' 

 64 45' 

 71 52' 

 77 25' 



No pleochroism was observed. Plane of axes a (100), obtuse bisectrix 

 normal to base. Double refraction +. Cleavage was observed on the base. 



RUBIDIUM URANYL, SULPHATE. 

 Rb 2 UO 2 (SO 4 )42H 2 O. 



The rubidium salt was more fluorescent than the potassium salt and mor 

 difficult to crystallize, so that measurements of it were not obtained. It is, 

 however, completely isomorphous with the potassium salt. The composition, 

 according to Rimbach, 4 is as above, with 2 molecules of water. 



1 Rimbach, I. c., 478. 



2 de Coninck, Bull. Acad. Roy. Belg., 1904, 1171; 1905, 50, 94. 



3 Ibid., 1905, 50. 



4 Rimbach, I. c., 479. 



