of Mineral Substances. 263 



A. 



1. A piece of cererit was heated to redness iu a platinum 

 crucible ; it lost 2 per cent, of its weight, and its original red 

 colour became brown : its form remained unchanged. 



2. 100 grains in fine powder, exposed for half an hour to a 

 strong red heat, lost 5 grains, and acquired a darker colour. 



B. 

 100 grains mixed with 200 of carbonate of potassa, and ig- 

 nited in a platinum crucible, shewed no tendency to fusion, but 

 assumed the appearance of a light brittle mass of an ash-grey 

 colour. Being saturated and washed, the filtered alcaline 

 liquor was colourless. It remained transparent when neutralized 

 with nitric acid, and therefore contained no oxide of tungsten ; 

 nor was any other acid present, since the solution was not af- 

 fected by the addition of solution of silver, mercury, lead, iron, 

 baryta, ^c. 



Tlie lixiviated residue was decomposed by repeated boiling 

 in nitric acid. After the separation of the silica, the nitric so- 

 lution was supersaturated with caustic potassa, boiled, filtered, 

 neutralised with muriatic acid, and mixed with carbonate of 

 potassa; but nothing was thrown down, nor did it become turbid. 

 C. 



a. 400 grains of the levigated fossil were digested in 4 ounces 

 of boiling muriatic acid, to which 1| ounces of nitric acid were 

 afterwards added. When every thing except the silica appeared 

 to be dissolved, the liquid was filtered off, and the residue, 

 washed and ignited, weighed 138 grains, 



b. The excess of acid in the straw-coloured solution was then 

 neutralized with liquid ammonia, taking care that nothing was 

 thrown down; succinate of ammonia was then added, which 

 caused a precipitate of succinate of iron, and which, after wash- 

 ing and ignition, afTorded 14 grains oi oxide of iron. 



c. The solution, thus freed from iron, was precipitated by 

 caustic ammonia; the oxide of cerium thus thrown down was 

 edulcorated and ignited ; it was of a brown colour, and weighed 

 218 grains. 



