416 Dr. Thomas Thomson and Dr. SteeVs [June 



Yttria . . . 1'94 or 5*5 

 Tartaric acid . 2-96 „ 8-25 

 Water. . . 0*36 „ 1*02 

 8. Phosphate of yttria.— Phosphoric acid does not dis- 

 solve yttria, but the phosphate may be obtained by precipi- 

 tating sulphate of yttria by phosphate of soda. The salt 

 falls in gelatinous flakes, having, when on the filter, much 

 the appearance of hydrate of alumina. After ignition it 

 still retains its opalescent appearance, but becomes more 

 compact, and of a vitreous lustre, though the particles are 

 not agglutinated. 



9-8 grs. of anhydrous sulphate of yttria gave 9*72 grs. of 

 hydrous phosphate, reduced by a red heat to 7*92 grs. 

 Now, as 9*8 grs of sulphate contain 5*133 grs. of yttria, we 

 have the constituents, 



Yttria 5*133 or 8*25 - \\ atoms. 



Phosphoric acid. . 2*786 „ 4*477 - 1 „ 

 Water 1*800 „ 2*8 - 2\ „ 



9*719 

 It is, therefore, a disesquiphosphate, apparently similar 

 to the native disesquiphosphate. 



IV. OF CERIUM. 



Cerium, as is well known, forms two oxides. We did 

 not succeed in our attempts to obtain the protoxide in a 

 separate state, but the salts containing it are readily formed. 

 The peroxide has a yellow or brown colour, according to 

 the mode in which it is obtained. Both oxides form salts 

 with acids. The salts containing the protoxide have an 

 amythystine colour, and are quite permanent. Those con- 

 taining the peroxide are yellow, or orange, and easily 

 decomposed. The sp. gr. of the peroxide of cerium is 5*33. 



The protoxide of cerium, when in the state of sulphate, 

 may be distinguished by the following characters : 



Prussiate of potash : A white chalky precipitate. 



Ammonia : A white gelatinous precipitate, not soluble 

 in an excess of ammonia. 



Potash : A white precipitate, insoluble in an excess. 



Alkaline carbonates : A white precipitate, soluble in an 

 excess, but precipitated again when boiled. 



