296 



ACCOUNT OF CERIUM. 



Acidulous ful- 

 phate of cerium 



Neutral acid. 



orange colour. By a flight evaporation of this folution, it 

 yields fmall, prifmatic, coherent cryftals, of the colour of 

 gold. This fait is an acidulous fulphate of cerium at a max- 

 imum. Thefe cryftals, thoroughly dried between blotting- 

 paper, and expofed to the air, are gradually reduced to a 

 yellow, almoft cryftalline powder. ReditToIved in water, 

 they experienced a decompolition ; a white powder is depo- 

 fited, and the folution becomes colourlefs. This white pow- 

 der is a fulphate of cerium, but little oxigenated. If tlie fo- 

 Acidulous ful- lution is evaporated to drynefs, it gives an acidulous fulphate 

 but fli\tiy"o3d-"^^^*^''"^^ ^''^ '^^^ oxigenated. Thefe cryftals are feldom cu- 

 bical, but almoft always prifmatic, ftriafcd and colledled in 

 bundles. Their tafte is four, but they aftervi^ards become fac* 

 charine and aftnngent. 



Treated with Houriatic acid, the yellow acidulous fulphate 

 of cerium yields part of its oxigen to the acid^ which is volatir 

 lized in oxigv^iated muriatic acid gas. The fait remains co- 

 lourlefs. An augmentation of temperature alone is fufficient 

 for the yellow acidulous fulphate of cerium to lofe its colour by 

 perature, which ^^^ ^^^ ^^^^^^ ^p j^^ oxigen. If the heat is increafed ftill 



aftf'.rwarcls arjves '^ ^ ^ 



off the acid, and more, the furplus of the acid is carried off, and a fat u rated 

 fulphate of cerium remains. By a continued calcination, it 

 regains oxigen, becomes red, and yields a fulphate of cerium 

 at a maximum. The fulphate of cerium, difoxigenated by tlie 

 muriatic acid, is more difficult to re-oxidate by calcination. 



In the humid way, the alkalies only decompofe the fulphate 

 of cerium incompletely. Ammonia precipitates an oxide 

 from the acidulous fulphate of cerium, which is only in a fmall 

 •quantity, but neverthelefs contains part of the fulphuric acid. 

 The fulphate of cerium is not perfe6tly decompofed, except 

 by calcination with three times its weight of carbonate of foda 

 or potafti. The calcined oxide is of a brown colour. By di- 

 geftion, ammonia can deprive it of part of its acid : the oxide 

 takes a diftindt flelh colour, which becomes brighter by dry- 

 ing. Digefted with concentrated muriatic acid, or with ni- 

 tric acid, a fmall quantity diffolves, having its yeHow colour. 

 Sulphate of ce- If a folution of acidulous fulphate of cerium is precipitated 

 riuman pota • j^^ p„ja(j^^ a triple combination of cerium, fulphuric acid, and 

 potafli, is feparated, before the acid is faturated. If too much 

 potafli is added, the combination is partly deftroyed. The 

 fulphate of cpriunj and potafl^, at a maxiviumi is pf an orange 



colour; 



genaccd. 



Muriatic acid 

 deprives the aci 

 dulous fulphate 

 of part of Its 

 oxigen : 

 As does an in- 

 creafe of tern- 



forms a neutral 

 ifuiphate. 

 Calcination re- 

 ftores the oxi- 

 gen. 



Action of the 

 alkalies on the 

 fulphates ot ce- 

 rium. 



