ACCOUNT OF CERIUM. 295 



Of the Properties of Oxide of Cerium. 



(B.) This oxide may appear in different degrees of oxida- The oxide is 

 tion. The alkalies precipitate a white oxide from its foliitions,"J'g*jj^*^jj° g^,^'^^ 

 which (hows of a yellowifli colour in the air, but, when per- oxidation. 

 ie&.\y dried, becomes dark. Expofed to a brifk and long- 

 continued fire, it takes a deep brick-colour. The oxalate and 

 acetate of cerium, calcined in velTels not completely clofed, 

 yield a white oxide, which, in an open fire, becomes of the 

 colour of bricks. It does not melt by itfelf. 



Treated with borax by the blow-pipe, it melts readily and Fufionwith 

 ("wells. The globule heated by the exterior flame, aflumes "^"* 

 the colour of blood ; which, by cooling, palTes to a yellowith 

 green, and at length becomes colourlefs, and perfectly tranf- 

 parent. Melted by the interior flame, thefe changes do not 

 take place ; it is then reduced into a colourlefs glafs ; but, ex- 

 pofed for a (hort time in the exterior flame, the fame pheno- 

 mena are produced. If too much oxide of cerium is made 

 ufe of, the glafs refembles an opake yellowifli enamel. Thefe 

 changes are more eafily manit'efted with the phofphate of foda 

 and ammonia. If two clear and colourlefs globules are melted 

 together, one of which was prepared with borax and the 

 other with the phofphate, they form a tranfparent glafs, which, 

 on cooling, becomes opake and pearl coloured. 



Thefe chara6lers, taken together, fufficienlly diflinguifh the 

 oxide of cerium from the oxide of iron. The latter alfo ofl^ers 

 the fame changes of colour, but its glafs, on cooling, has a 

 deep green colour, Vjhich fades. The globules made with 

 borax and the phofphate melted together, yield an opake 

 glafs, the colour of which is a little deeper. 



Oxide of Cerium treated with Sulphuric Acid. 



(C.) When oxide of cerium is digefled with fulphuric acid. Sulphate of ce- 

 thefe two fubftances unite, and the refult is a red infoluble '^'"'^ ^l ^ *"/*'' 

 fait, which is fulphate of cerium at a maximum of oxidation, fion. 

 If the acid is concentrated, it fcarcely diflTolves any of it. If 

 it i& diluted with half its quantity of water, or a little more, 

 the refult is a yellowifli oily liquor, which does not adhere to 

 the glafs, nor does it wet it. If the acid is mixed with fix or 

 feven times its quantity, or even more, of water, and em- 

 ployed in a fufficient quantity, the , oxide is diflolved of an 



orange 



