URANIUM SALTS. 



121 



nitrate obtained from an alcoholic solution would light of wave-length 

 greater than k 4900 excite phosphorescence? 



Different salts of uranyl phosphoresce very differently. The speci- 

 mens of uranyl chloride gave very weak and diffuse bands. Uranyl nitrate 

 obtained from the evaporation of a methyl alcohol solution showed no phos- 

 phorescence. Uranyl bromide also gave very little phosphorescent light 

 on excitation. Using the Hilger spectroscope, the following approximate 

 wave-lengths for bands of various salts were found: 



Uranyl sulphate . 

 Uranyl nitrate . . 

 Uranyl acetate . . 



5660 5580 

 5670 5600 

 .... I 5570 



5420 

 5410 



5315 

 5330 

 5340 



5210-5160 5085 4950 

 5180 5100 | 4970 

 5070 



4860 

 4840 



The bands are so hazy and wide that these measurements mean very 

 little. 



Very little has been done on the fluorescence of solutions of uranyl 

 salts. Some work by Stokes, Becquerel, Morton and Bolton, and others 

 treats of fluorescent bands. Morton and Bolton give the following wave- 

 lengths for some of the fluorescent bands of the solid salts: 



Uranyl acetate, solid 



Uranyl chloride, solid 



Uranyl monophosphate, solid. . . 

 Uranyl monophosphate, in solu- 

 tion 



Uranyl sulphate 



Uranyl sulphate, anhydrous. . . . 



6240 

 6300 

 6510 



6470 

 6520 

 6580 



6070 5760 



6000 

 6170 



6200 

 6150 

 6230 



5660 

 5850 



5910 

 5870 

 5930 



5500 

 5400 

 5600 



5650 

 5600 

 5630 



5240 

 5180 

 5200 



5380 

 5340 

 5365 



5030 

 4930 

 5100 4880 4720 



5160 

 5110 

 5145 



4920 4800 

 4890 4770 



4850 



4780 



URANOUS SALTS. 



Uranium was discovered in 1789 by Klaproth and was named to com- 

 memorate the discovery of the planet Uranus by Herschel in 1781. Quite 

 a large number of oxides are known. 



The orange oxide, U0 3 (U0 2 0), or uranyl oxide is obtained by heating 

 uranyl nitrate slowly as long as acid fumes escape. When the nitrate is 

 rapidly decomposed a red modification of the oxide is produced. All the 

 uranyl salts may be considered as compounds of U0 3 , where one of the 

 oxygen atoms has been replaced by an acid or halogen radical. Aqueous 

 solutions of the uranyl salts are partly hydrolyzed. The non-hydrolyzed 

 portion dissociates in the usual way. 



Urano-uranic oxide (U 3 8 ) is obtained by heating uranyl nitrate to a 

 high temperature. 



The oxide U0 2 is obtained by heating U 3 8 in a current of hydrogen, 

 and is of a brown or copper-red color. The reduction of an oxide of uranium 

 to U0 2 and weighing is an analytical method of estimating uranium. This 

 oxide in acid solutions forms the green uranous salts. 



The oxide U 2 5 is formed when ammonium uranate is strongly ignited 

 in air. U0 4 is formed when a dilute solution of hydrogen peroxide is added 

 to uranyl nitrate. The uranates have the general formula R 2 U 2 7 , as, for 

 example, potassium uranate, K 2 U 2 7 . When alcohol is added to a solution 



