374 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The hydrated uranyl bromide is more easily obtained. The green 

 oxide was reduced by hydrogen to urauous oxide, suspended in water, 

 and heated with bromine on the steam bath. After driving off the 

 excess of bromine, uranyl bromide remains in solution. The solution 

 may be evaporated to the consistency of a thick syrup, and even under 

 the best conditions the yield of crystals is very small. Moreover, it is 

 almost impossible to wash the crystals free from the mother liquor, 

 since they are extremely soluble in water and alcohol, and ether decom- 

 poses the compound, setting free bromine. Hence uranyl bromide was 

 abandoned. 



Of the iodine compounds of uranium, the iodate alone seemed promis- 

 ing. This compound has been prepared and described by A. Ditte,* 

 who assigns to it the anhydrous formula U0 2 (I0 3 ) 2 . The iodate was 

 prepared by us as follows : — 



To a solution of uranyl nitrate, containing much nitric acid, was added 

 a solution of iodic acid, prepared by warming finely powdered iodine 

 with nitric acid of specific gravity 1.50. Both solutions were heated to 

 boiling before mixing. Uranyl iodate is precipitated as a yellow, finely 

 crystalline salt, but slightly soluble in water at ordinary temperatures. 

 At 100°, however, if some nitric acid is added, it is possible to obtain 

 a solution containing ten grams of iodate to the litre. On cooling, 

 2.5 to 3.0 grams of iodate crystallize out. By recrystallizing a few 

 times, in sufficiently large vessels, it is possible to obtain a compound in 

 a high state of purity. 



The method of preparation described above is that recommended by 

 Ditte. Although Ditte's course of procedure was carried out as ex- 

 actly as possible, the compound obtained differed from that which he 

 describes. Instead of being anhydrous, it contained one molecule of 

 water. Inasmuch as Ditte's statement of the amount of nitric acid 

 which he used is extremely vague, different concentrations were tried, 

 from a solution slightly acid up to one containing twenty-five per cent of 

 strong nitric acid. In every case the hydrated compound was obtained. 

 Ditte did not recrystallize his compound, but our recrystallized product 

 was identical with that which was only once precipitated. The analysis 

 given is the average of ten concordant analyses of material prepared 

 from both hot and cold solutions. Both recrystallized iodate and that 

 precipitated only once are represented. The method of analysis is 

 described below. 



* Annales de Chimie et de Physique, 6th Series, 21, 158 (1890). 



