1825.] M. Berzelius on Uranium. Til 



To ascertain whether it had carried down any portion of oxide 

 of uranium, it was dissolved, with the assistance of a boiUng 

 heat, in dilute muriatic acid, by which a white powder, consist- 

 iiig of sulphate of barytes, remained undissolved. The acid 

 solution was precipitated neither by ammonia nor by triple 

 prussiate of potash : the gypsum had therefore contained no 

 oxide of uranium. The alcoholic solution was evaporated to 

 dryness, and the residue was strongly ignited with carbonate of 

 soda; the fused mass was then digested in water, which 

 extracted phosphate of soda, and left a compound of oxide of 

 uranium and soda undissolved. The latter was dissolved in 

 muriatic acid, precipitated with caustic ammonia, washed vi^ith a 

 solution of sal ammoniac, dried, ignited, and weighed. Muriatic 

 acid did not dissolve from it a trace of oxide of uranium. The 

 alkaline solution, on being saturated with munatic acid, let fall 

 a minute white coloured precipitate, which proved to be a mix- 

 ture of neutral phosphate of oxide of uranium and phosphate of 

 oxide of tin. The filtered liquid was boiled, in order to expel 

 the carbonic acid gas, and precipitated by a mixture of ammonia 

 and muriate of lime ; the phosphate of lime was afterwards 

 washed, ignited, and weighed. 



2. The nitric solution of the ignited mineral was precipitated 

 with a slight excess of acetate of lead ; its yellow colour by this 

 treatment became much paler, but did not completely disappear. 

 The precipitate, which was a double phosphate of the oxides of 

 lead and uranium, and which contained the whole phosphoric 

 acid of the mineral, was washed, ignited, and weighed. It was 

 then dissolved in nitric acid, the solution was mixed with rather 

 more sulphuric acid than was necessary to precipitate the oxide 

 of lead, and evaporated until most of the nitric acid was dissi- 

 pated. Alcohol now added precipitated the whole of the sul- 

 phate of lead, which was washed, ignited, and weighed. The 

 remaining liquid contained phosphoric acid and oxide of uranium, 

 together with some sulphuric acid. Potash separated from it 

 the oxide in the state of uranate of potash ; the precipitate was 

 dissolved in muriatic acid, and the oxide was again thrown 

 down by ammonia, washed with a solution of sal ammoniac, 

 and ignited. The quantity of phosphoric acid was deduced by 

 subtracting from the weight of the double phosphate that of the 

 oxide of lead contained by the sulphate, and that of the oxide of 

 uranium which was equivalent to the obtained quantity of 

 oxidule. The original solution which had been precipitated 

 with acetate of lead, still retained about one-tenth of the oxide 

 of uranium. The excess of oxide of lead was removed by sul- 

 phuretted hydrogen gas, and from the filtered liquid. The 

 oxide of uranium was precipitated by ammonia. The barytes 

 was now separated by a few drops of sulphuric acid, and the 

 remaining liquid, after having been evaporated nearly to dryness, 



