230 FLUORESCENCE OF THE URANYL SALTS. 



This was recrystallized from water and left microscopic plates with wide black 

 edges, as on a crystal lying on 6 (010) and bounded by m (110) and c (001), or 

 else having a very high index, a low double refraction, and straight hyper- 

 bolas, as from a tipped uniaxial crystal or near an optic axis. 



DOUBLE URANYL TARTRATES. 



The tartrates are exceedingly soluble, and likely to result in gums on 

 drying, which do not crystallize. The existence of a sodium double salt in 

 solution is indicated by the work of Grossman 1 and Loeb on the effect of heavy 

 metals on the rotation of tartaric acid. The potassium double salt is de- 

 scribed by Frisch 2 and the antimonyl salt by Peligot (see uranyl tartrate), 

 but none of the salts show fluorescence, so they were not taken up further. 

 The corresponding molybdyl and tungstyl compounds were attempted, since 

 the oxides are soluble in tartaric acid, but only thick gums which did not 

 crystallize or fluoresce were obtained. 



POTASSIUM URANYL TARTRATE. 



This salt, described by Frisch, was prepared by Cragwall by adding uranyl 

 nitrate to potassium tartrate and washing free from nitrates. Since Frisch 

 produced his material by dissolving precipitated uranyl hydroxide in acid 

 potassium tartrate (Weinstein) and found that it could not be crystallized by 

 drying, but was precipitated by alcohol, it seems probable that the material 

 which Cragwall obtained on washing was simply the acid potassium tartrate 

 itself. Examination for fluorescence and under the microscope indicated 

 this. 



ANTIMONYL URANYL TARTRATE. 



UO s .(SbO.C 4 H4O,),4H 2 O. 



This is produced, according to Peligot, by adding uranyl nitrate solution to 

 potassium antimonyl tartrate solution. Cragwall washed the precipitate free 

 from nitrates. The resulting material appeared to be amorphous and showed 

 no fluorescence. In this case both basic radicals are commonly in the complex 

 anion, so that it is difficult to decide which comes first. 



POTASSIUM URANYL PROPIONATE. 

 K UO2(C 2 H 6 2 )3. 



Rimbach 3 examined the potassium and ammonium double salts with pro- 

 pionic acid and the potassium double salt with butyric and valerianic acids. 

 These crystallize in tetrahedra, according to Sachs, 4 but were not attempted 

 for this work. 



1 Grossman and Loeb, Z. Phys. Chem., 72, 93. 1910. 



2 Frisch, J. Prakt. Chem. 97, 281. 1866. 



3 Rimbach, Ber., 37, 484. 1904. 



4 Sachs, Ber. 37, 484. 1904. 



