CHEMISTRY OF FLUORESCING URANYL SALTS. 225 



Zehenter 1 gives 1/2 H 2 0. Since the isomorphous ammonium salt is without 

 water, and since both potassium acetate and uranyl acetate are hygroscopic 

 and the salt occurs in needles, it seems likely that the water is not in the 

 crystals. The crystals are mostly prism and pyramid of the tetragonal system, 

 with the axial ratio a:c = 1: 1.2831, according to Schabus. The specific 

 gravity is given by Zehenter as 2.396. The best crystals were obtained by 

 slow cooling, the tendency being to form needles. It was prepared by dis- 

 solving weighed potassium carbonate in an excess of acetic acid and adding the 

 required amount of uranyl acetate. 



AMMONIUM URANYL ACETATE. 

 (NH 4 )U0 2 (C 2 H 3 2 )3. 



This salt was prepared and measured by Rammelsberg, 2 who found 

 the axial ratio 1: 1.4124 in the tetragonal system apparently isomorphous 

 with the potassium salt. Grailich and Schrauf 3 assigned 1 molecule of water 

 to this salt, but Rammelsberg denies this. Zehenter gives the specific gravity 

 as 2.219. This was prepared by Cragwall by crystallizing equal molecular 

 quantities of the two salts together. 



RUBIDIUM URANYL ACETATE. 

 RbUO 2 (C 2 H 3 02)3.?H 2 O. 



This salt was prepared by crystallizing uranyl acetate in calculated amount 

 with rubidium acetate produced by evaporating off rubidium chloride several 

 times with acetic acid. On cooling, tetragonal needles separated out, but on 

 further evaporation the uranyl acetate separated, leaving the rubidium acetate 

 in solution. The crystals were measured, giving an angle o:m = (111): 

 (110) = 2633', which corresponds to an axial ratio of a: c = 1: 1.4151. 



SILVER URANYL ACETATE. 

 AgUO 2 (C 2 H 3 O2)3H 2 O. 



This salt was prepared and measured by Wertheim, who found it tetra- 

 gonal, with an axial ratio of 1.5385. He assigns 1 molecule of water of 

 crystallization, which seems doubtful. This was prepared from calculated 

 quantities of uranyl acetate and silver acetate dissolved in aqueous acetic 

 acid. If left in the light the solution decomposes, which resulted in many 

 of the crystals being covered with a black coating of silver. These crystals 

 are more inclined to be granular. 



LITHIUM URANYL ACETATES. 

 LiUO 2 (C 2 H 3 O 2 ) 3 3H 2 O. 



This is given by Wyrouboff 4 as crystallizing in the monoclinic system with 

 the axial ratio a: b: c = 1.2647: 1: 1.5849; /3 = 9953'. It forms readily on 

 crystallization of water solution of the two acetates, but does not give very 

 good crystals. The other hydrate, LiUC^^HsC^sSH^O, with forms below 

 15 was not obtained. The solution was made by adding to weighed lithium 

 carbonate which had been treated with an excess of acetic acid a calculated 

 amount of uranyl acetate. This was put in a desiccator over dehydrated 

 potassium acetate in an unheated room in winter, but the SH^O phase was 

 not found. 



1 Zehenter, Monatsh. f. Chem., 21, 235. 1900. 



2 Rammelsberg, Sitz. ber. Acad. Wiss. Beri. 1859. 



3 Schrauf, Sitz. ber. d. Acad. Wiss. Wien, 41, 779. 1860. 



4 Wyrouboff, Bull. Soc. fran. Min., 8, 115. 1885. 



