ANALYSIS. 251 



one hour. They weighed, xi-hilfifiUl ivarm, 35| graio"?, which Defcnption and 

 is a lofs of 2St per cent. 25 grains of the fame parcel, from =*".^'y'»s of a 

 1 • 1 T 1 . t . r r , , ,- , mineral from 



Which 1 had taken the fonner, expoled to a heat ot longer Cornwall. 



continuance and greater intenfity, were diminiflied in weight, 

 at the rate of .^0| per cent. 



(2.) The powder (liil preferved Its pure whitcncfs. It 

 was transferred into a matrafs, and nitric acid poured upon 

 it, which foon began to a<5t upon it. The matrafs was 

 placed, for many hours, in a digefting heat» A folution of 

 the whole of the fubftance, except a fmall portion, was ef- 

 fedted. I added a few drops of muriatic acid, and continued 

 the digeftion. 



(3.) The acid was now diluted with diflilled water, and 

 poured off from the refiduum, which confided partly of a fine 

 fpongy earth, and partly of fragments of quartz. It was 

 eaught on a filter and fuffici^ntly edulcorated. The laft por- 

 tion of edulcorating water dropped through the filter of" an 

 epalifti hue. 



The refiduum, dried and expofed to a red heat, for ten 

 minutes, = ^^ of a grain, -^ of which confifted of fragments 

 of quartz, -j— was found to be filica, and -^ alumina. 



(1.) The clear folution and edulcorating water were poured 

 into a large matrafs and boiled, and whilfl boiling, the con- 

 tents were precipitated, in white flakes, by ammonia 



(2.) When the ammonia had ceafed to produce any further 

 precipitate, the clear fluid was decanted, and affayed with 

 carbonate of ammonia. But its tranfparency was not in the 

 leafl dlHurbed. 



(3.) This clear fluid, together with the edulcorating water, 

 with which the fubfided precipitate had been wafiied, was 

 gradually evaporated. When its volume was confiderably di- 

 miniflied, a reparation of a fpongy earth took place, more 

 Qopioufly than I had reafon to expeft, and the quantity of it 

 was flill further increafed by a few drops of ammonia. This 

 earth, thus feparated, was fufficiently edulcorated, and added 

 to the former precipitate. 



(4.) The fluid was again evaporated, and at laft transferred 



to a crucible of platina, and the fait reduced to a dry ftate : on 



rediflblving this fait in diftilled water, a minute portion of 



2 eerihy 



