282 Experiments upon Green Vran Mica, [Apkil, 



matter, easily separable by washing, are sometimes found adhering 

 in small quantities to them. 



The purest pieces were carefully selected for experiment. 



The specific gravity of this fossil, taken at the temp. 52 of Fahr. 



was 3 3. 



A portion of it, reduced to a fine powder, was exposed, in a 

 small glass retort, to an open fire. A dew soon collected on the 

 neck of the retort, and passed into the receiver. It was pure 



water. 



100 grains, that had been exposed to a low red heat for ten 

 minutes in a platinum crucible, weighed whilst still warm = 84*6. 

 The mineral, therefore, had lost 15 4 per cent. Another portion 

 exposed to a stronger heat for one hour was diminished, in respect 

 of weight, very nearly in the same proportion. 



The mineral, after ignition had lost its brilliancy, and had 

 assumed the appearance of fine brass filings. 100 grains, which 

 had not been ignited, in the state of a fine powder, were put into 

 a matrass, and covered with pure nitric acid, moderately diluted 

 with water. The acid produced no effervescence, and whilst it was 

 unaided by heat, it seemed to act very feebly upon the mineral for 

 many hours. The vessel was then placed in a digesting heat. Yet 

 the solution proceeded very slowly, and was frequently interrupted 

 by the deposition of a green crust, which from time to time covered 

 the bottom of the vessel, and protected the mass from the action of 

 the acid. Boiling water produced little or no change on this crust. 

 It became necessary, therefore, repeatedly to add fresh portions of 

 nitric acid in order to dissolve it. At last, by means of an excess 

 of acid, a solution of the mineral was effected, except a very small 

 quantity of residuary matter, which after ignition = 0-1 gr. It 

 was a mixture of quartz and oxide of iron ; and as it was extra- 

 neous, I dissolved an equal quantity (O'l gr.) of pure uran mica in 

 nitric acid, and added the solution to the former one. 



The solution was light green, 1 now poured into it ammonia in 

 excess, which separated a yellowish- while matter. The blue super- 

 natant fluid was carefully poured off from the subsided precipitate, 

 and fresh portions of ammonia were repeatedly supplied, and the 

 mati'ass containing it was from time to time shaken, and at last 

 exposed to a digesting heat. 



When the last eliUsions of ammonia, aided by the heat of the 

 sand-bath, showed not the slightest iridications of copper, but were 

 poured off absolutely colourless,* the undissolved matter was mixed 

 with distilled water, and thrown upon a filter, and sufficiently 

 edulcorated. \\ hat was thus separated by the filter was gradually 



• 'Wlien in a former analysiis I operated upon the same quantity of iiran mica 

 wliich had been ignilccl, I fomid that the last portions of ammonia, ^vhen tliej hail 

 cp.x^ed to be tinned hliie, heeame of an opal hue, and that a edtiHilernble qu.intitT 

 of di.-tilled water passed through the filler before It became pert'eetly transparent, 

 hi this case nearly two per cent, of uran o.xide were suspended by the ammonia. 

 / 



