422 Dr. Thomas Thomson and Dr. Steel's [June 



A little sulphuric acid may have been driven off by the 

 previous ignition. The result is, however, sufficiently near 

 to prove the composition of the salt to be, 



1 atom sulphate of cerium . . 11*5 

 1 „ „ potash . . 11*0 



22-5 



6. Potash-sesquisulphated peroxide of Cerium. — A beautiful 

 yellow powder, becoming white when washed or heated. 



4*8 grains lost by gentle ignition 0*5 grs. The residue 

 was dissolved in muriatic acid, and the oxide of cerium was 

 thrown down by ammonia. The remaining liquor evapo- 

 rated to dryness, left 1*8 grs. of sulphate of potash. 

 It is clear from this that the salt is a compound of, 

 1 atom sesquisulphated peroxide of cerium, 

 1 atom sulphate of potash. 



7. Oxalate of Cerium. — This salt may be obtained by 

 adding either oxalic acid or oxalate of ammonia to a solu- 

 tion of sulphate of cerium. When oxalic acid is used the 

 salt falls down like a piece of curd, perfectly white, and it 

 may be taken out of the vessel in a lump on the end of a 

 glass rod. It is very adhesive and plastic, exactly like so 

 much soft resin. Whether allowed to remain in the solu- 

 tion or dried, it rapidly loses this property, and falls to a 

 white powder. When heated it burns and leaves pure per- 

 oxide of cerium. 



After having been dried in the highest temperature it 

 could bear without charring, 28*15 grs. left, on ignition, 

 17*9 grs. of peroxide = 16*62 protoxide. Supposing the 

 salt to have been perfectly anhydrous, we have its com- 

 position, 



Protoxide of cerium . . 16*62 or 6*492 - 1 atom. 



Oxalic acid 11*53 „ 4*5 - 1 ,, 



28*15 



8. Sesqui-oxalated peroxide of Cerium. — This salt may be 

 obtained from the solution of the peroxide, exactly in the 

 same manner as the last salt. The adhesive matter obtained 

 is reddish-yellow, instead of white, but it falls into a white 

 powder when dried. 



20*6 grs. digested in caustic potash for 12 hours left 10 



