1823.] Mr. R. Phillips 's Analysis of 'Uranite.. 59 



question had been dissolved in nitric acid, it was evident that 

 the yellow precipitate could not be arsenite of silver. 



As phosphoric acid is well known to afford ayellow precipitate 

 with oxide of silver, I suspected the presence of this acid, and 

 I found that the alkaline solution gave a blue precipitate with 

 sulphate of copper; and when it was saturated with an acid, 

 mixed with ammonia and muriate of magnesia, the well-known 

 minute crystals of phosphate of ammonia and magnesia were 

 formed. 



Under these circumstances, it appeared to me worth while to 

 subject the uranite to another analysis, and I proceeded as 

 follows : 



One hundred grains of the green uranite of Cornwall were dis- 

 solved in dilute nitric acid; half a grain of silica remained 

 undissolved. In attempting to saturate the solution previously 

 to adding nitrate of lead for the separation of the phosphoric 

 acid, I found that precipitation occurred long before sufficient 

 potash had been added. As this free nitric acid would dissolve 

 the phosphate of lead formed, I decomposed the nitric solution 

 by boiling it with excess of potash, and then having added 

 excess of acetic acid to the alkaline solution, nitrate of lead gave 

 an abundant precipitate of phosphate. I prefer acetic acid for 

 this purpose to nitric, because as acetic acid has scarcely any 

 action upon phosphate of lead, it is not requisite to take the 

 trouble of avoiding slight supersaturation. 



The phosphate of lead thus obtained, after washing and dry- 

 ing, weighed 80 grains, equivalent, according to Dr. Thomson, 

 to 16 grains of phosphoric acid ; the oxides of uranium and 

 copper were redissolved in nitric acid, and the solution being 

 added to ammonia, the oxide of copper was dissolved, and that 

 of uranium precipitated ; the latter, after washing and drying, 

 weighed 60 grains, and the oxide of copper, after ebullition with 

 potash, weighed 9 grains. The ammoniacal solution contained 

 no lime. It appears, therefore, that 100 grains of this substance 

 contain 



Silica 0*5 



Phosphoric acid 1 6*0 



Oxide of uranium 60 - 



Oxide of copper 9*0 



Water 14-5 



100-0 



I attempted to determine the quantity of water by direct 

 experiment ; for this purpose 50 grains of the mineral were 

 heated on a platina crucible by a spirit lamp, 8*5 grains were 

 lost = 17 per cent. This experiment was repeated with a pre- 

 cisely similar result, and no further loss was occasioned by 

 exposing the mineral to a strong red heat. If, however, we add 

 17 to the acid and oxides, there will be an excess of 2'5 over 



