CHEMISTRY OF FLUORESCING URANYL SALTS. 223 



URANYL ACETATE DIHYDRATE. 



This salt was prepared by Crag wall by recrystallizing the anhydride from 

 water solution. There was also a stock of material from Kahlbaum and un- 

 known sources. In an attempt to recrystallize this salt in large, clear crystals 

 much difficulty was met, as it usually fills with cracks as it grows. The best 

 material, having as much as 4 mm. cube of clear material, was obtained by 

 supersaturating 2 grams in 200 c.c. and allowing a month or two to crystallize. 

 The crystal properties were found to be similar to those described by Schabus, 1 

 the system being rhombic, with an axial ratio of 0.7817: 1: 0.3551, with the 

 forms TO (110), a (100), r (101), n (120), and b (010). The prism zone is very 

 much striated, affording a continuous procession of reflections in the gonio- 

 meter. Schabus finds cleavage on m, a, b, c, which accounts for their extreme 

 friability. Zehenter 2 finds the specific gravity to be 2.893. The refractive 

 index was determined through the dome as being 1.490 for light vibrating 

 parallel to the c axis and 1.521 parallel to b. 



The uranyl acetate trihydrate, which, according to Schabus, forms below 

 10 C., was not prepared. It crystallizes in the tetragonal system with an 

 axial ratio of a : c = 1: 1.4054. 



DOUBLE URANYL ACETATES. 



The sodium salt occurs in the acetates as well as the sulphates and is the 

 only uranyl salt crystallizing in the regular system. The ammonium and 

 potassium salts seem to be isomorphous, in spite of the fact that the potassium 

 salt is said to contain 1 molecule of water and the ammonium salt to be anhy- 

 drous. The silver salt, which contains 1 molecule of water, is apparently 

 isomorphous and the rubidium salt was found to have a similar axial ratio, as 

 usual very near that of the ammonium salt. The similarity of axial ratio 

 to that of the uranyl nitrate trihydrate suggests that these salts form a group 

 that might well be studied further. The caesium salt could not be obtained, 

 the uranyl dihydrate crystallizing out and leaving the caesium acetate in 

 solution. The two hydrates of lithium uranyl acetate fully described by 

 Wyrouboff 3 as being monoclinic were attempted, but only the room-tempera- 

 ture form was obtained. The double salts of uranyl acetate with bivalent 

 acetates were in general prepared by dissolving the oxide or carbonate of the 

 second metal in acetic acid in excess, adding uranyl acetate in calculated 

 amount, with water enough for complete solution, and allowing to crystallize 

 by slow evaporation. Difficulties were encountered in the preparation of 

 some of the salts, such as the calcium salt, which Rammelsberg also could not 

 obtain, as described by Weselsky, 4 which was finally prepared by Weselsky 

 method of precipitation with calcium carbonate and solution of the precipitate 

 in acetic acid. The barium salt was finally prepared by this method. The 

 cadmium was never prepared at all; at least, no specimen that gave anything 

 but the uranyl-acetate spectrum. An attempt to produce a mercuric acetate 

 also failed. 



1 Schabus, Prieschr. Wien, 207. 1855. 



2 Zehenter, Monats f. Ch., 21, 235. 1900. 



3 Wyrouboff, Bull. Soc. fran. min., 8, 115-122. 1885. 



4 Weselsky, J. Prakt. Chem., 75, 55. 1858. 



