ACCOUNT OP CERIUM. ^97 



colour ; that which is at a minimum, is white. A fimilar com- 

 bination is alfo obtained by pouring muriate of cerium into a 

 folution of lulphate of potafli. Sulphate of ammonia does not 

 form any precipitate in it ; but, on adding a calcareous fait 

 to it, fulphate of cerium combined with potafli is rapidly 

 depofited. 



Thefe chara6lers offer a ready method of feparating the ful- Sulphuric acid 

 phale of cerium from iron. It muft however be obferved, ^^j j^^^^g ^^'^^.^^ 

 that when the folutions are faturated, a little iron is alfo de- um from iron, 

 pofited, which gives a yellow colour to the precipitate; but 

 by adding a little fulphuric acid in excefs, the iron is redif- 

 folved, and leaves the precipitate entirely white. This com- 

 bination is only didblved in part by dilute fulphuric acid, and 

 the greateft quantity of that feparates afterwards. 



The lulphate of cerium and potalh melts by a flrong heat. Sulphate, zni 

 Feated with charcoal, it gives fulphuret of potafli and ful- 

 piiuret of cerium. Melted with carbonate of potafli, in clofed carbonate of cc- 

 vefiels, it yields carbonate of cerium and fulphate of potafli. '^^""** 

 This fait contains only one-third of oxide of cerium. 



It is diflblved in concentrated nitric acid, and, during the Concentrated 

 cooling, an acid fait, formed of acidulous fulphate of potafli"^^**^ J^^^^j-^j*;' 

 and a little fulphate of cerium, cryftallizes. Thus the fulphate phate of cerium 

 of cerium combined witii potafli, is decompofed by concen- *"^ P°^^^* 

 trated nitric acid. This ac id carries off the metal, and the 

 fuiphuric acid is directed wholly upon the potafli, with which 

 it forms a fait with excefs of acid. 



Qxide of Cerium with Nitric Acid. 

 (D.) Nitric acid diflblves the calcined oxide with difficulty, Nitrate of ccri- 

 but that which is precipitated by pure or carbonated alkalies, 

 with eafe. When the folution is faturated with oxigen, it is 

 of a greenifli yellow colour ; but colourlefs, when lefs oxided. 

 Evaporated to the confiftence of honey, it depofits lamellated 

 cryflals, which atlrad the humidity of the air. The folution 

 has a faccharine tafte : like all the other faturated folutions of 

 cerium, it lets fall an oxide of cerium, at a maximum of oxi-. 

 llation, in the open air. This precipitate is frequently formed 

 of oxide of iron. When dry, this fait is of a yellovvilli white 

 colour ; but becomes colourlefs on being diflfolved in a fuffi- 

 • (cient quantity of water. |t difl'oives readily in alcohol. 



4 A con- 



