LANTANUM. 645 



ammonia added to the liquid, which throws down a mixture of 

 cerous and eerie oxides. The oxides of cerium are reduced with 

 difficulty, but by decomposing the cerous chloride by potas- 

 sium, the metal was obtained by Mosander as a pulverulent 

 mass of a dark chocolate brown, which gave a grey metallic 

 trace under the burnisher. It oxidates quickly in water, disen- 

 gaging hydrogen gas, particularly when the water is a little heated. 



Protoxide of cerium, Cerous oxide, Ce O, is procured by cal- 

 cining the mixed oxides of cerium, obtained as already described, 

 by precipitating the solution of cerite in an acid by ammonia, 

 till chlorine is no longer disengaged, as perceived by its odour. 

 The salt that remains, when dissolved in water and precipitated 

 by an alkali, gives the hydrate of cerous oxide, which soon 

 becomes yellow in the air. The cerous salts are generally co- 

 lourless, although some of them have an amethystine colour, 

 like the salts of manganese. Their taste is sweet and afterwards 

 astringent and they greatly resemble the salts of yttria. From 

 these they may be distinguished by forming a salt with sulphate 

 of potash of small solubility. They are precipitated white by 

 the yellow prussiate of potash, not affected by sulphuretted 

 hydrogen, and precipitated by an alkaline sulphuret with dis- 

 engagement of sulphuretted hydrogen gas. 



Peroxide of cerium, Ceric oxide, Ce 2 O 3 , is obtained by cal- 

 cining the cerous nitrate or carbonate. The ignited oxide is 

 brick red and pulverulent, easily soluble in acids, from which it 

 is thrown down by an alkali as a mucilaginous matter, of a 

 clear .yellow colour, which is the hydrated oxide. This hydrate 

 is not soluble in caustic alkalies, but alkaline carbonates dissolve 

 a small quantity of it and become yellow. An intermediate 

 compound, the ceroso-ceric oxide, is obtained when eerie oxide 

 is exposed to hydrogen at a red heat. It is a lemon yellow 

 powder, which passes into eerie oxide by combustion in air. 

 The salts of eerie oxide are distinguished from those of cerous 

 oxide by their yellow and sometimes orange colour, by their 

 taste which is sweetish-sour and strongly astringent. They are 

 decomposed when boiled with hydrochloric acid, and converted 

 into cerous salts with evolution of chlorine. 



LANTANUM. 



The oxide of this new metal was lately discovered by Mo- 

 sander to exist in the cerite of Bastnas, forming indeed two 



