246 Intelligence and Miscellaneous Articles. 



ON THE COMPOSITION OF THE ARSENIATES OF URANIUM. 

 BY M. WERTHER. 



The author observes that arsenic acid acts like phosphoric acid on 

 the oxide of uranium. It is easy to obtain salts with one or two 

 equivalents of metal ; as to trisalt, M. Werther cannot positively 

 affirm that it exists. 



To analyse these arseniates, the author dissolved them in hydro- 

 chloric acid, then boiled with sulphurous acid, and precipitated the 

 arsenic by sulphuretted hydrogen ; the filtered solution was after- 

 wards precipitated by ammonia, as in other analyses. He always ob- 

 tained more exact results by estimating the arsenic acid by difference. 



The arseniate with one equivalent of uraniumjs obtained by eva- 

 porating the oxide of the nitrate or acetate of uranium with an ex- 

 cess of arsenic acid, and allowing it to remain over sulphuric acid. 

 The salt then appears in small crystals grouped together, but which 

 are not measurable, It is soluble in mineral acids and carbonate of 

 ammonia, insoluble in acetic acid and in water. When strongly 

 calcined it yields anhydrous arsenic acid, oxygen and a subsalt, the 

 composition of which has not been determined. 



If the solution of the salt in arsenic acid be treated with ammonia, 

 a bright yellow precipitate is obtained which contains ammonia. 



This salt yielded by analysis, — oxide of uranium, 48'17 ; water, 

 13-7. Heated to 302°' F. the salt lost 9*2 to 10-8 per cent, of water, 

 which agrees with the formula [As- O 5 , 2H 2 O, U 2 O 2 0, + 3 aq]. 



The diarseniate of uranium, like the corresponding phosphate, may 

 be obtained by different processes. 



a. By adding arsenic acid to acetate of uranium, washing the 

 pale yellow precipitate, and drying it over sulphuric acid. The pro- 

 duct is insoluble in water and in acetic acid. Analysis : — oxide of 

 uranium, 59*05 ; water, 172 ; it loses at 248° F. 15*07 per cent, of 

 water. These results agree with the formula 



[As 2 0\ H 2 O, 2U 2 O 2 O + 8 aq] . 



b. When nitrate of uranium is boiled with arsenic acid till a good 

 part of the nitric acid is expelled, on water being added to the 

 liquid, a yellow powder separates, which, when completely washed 

 and analysed, gives the same composition as the preceding. 



c. If a solution of biarseniate of potash be added to one of nitrate 

 of uranium, a pale yellow crystalline powder separates. This salt 

 always contains potash, but not as much as an equivalent. Analysis : — 

 water by calcination, 11*3 ; at 266°, 10*5 ; oxide of uranium, 60*85 ; 

 jjotash, 2*7. The calcined salt contains 67*84 per cent, of oxide of 

 uranium, and 3*6 per cent, of potash. 



If an excess of trisarseniate of soda be added to a solution of ni- 

 trate of uranium, a pale yellow powder separates, and the liquid con- 

 tains no uranium. The precipitate appears viscid, and passes through 

 the filter during washing. It must therefore be washed with a so- 

 lution of sal-ammoniac, and then with weak alcohol. 



This salt contains — soda,5*91 ; oxide of uranium, 60*21 to61'13; 

 water, 9*91 ; that is to say [As 2 0\ Na 2 0, 2U 2 O 2 + 5 aq]. It is 

 therefore a sodio-arseniate of uranium.-— Journ. de Ph. et de Ch., 

 Juillet 1848. 



