rite. 



332 EARTHS PROPER. 



vious, that one third of this surplus, or O0667 

 belongs to that portion ; we have, therefore, 

 0*1335 grain to subtract from the 17*14, to 

 obtain the quantity of silica in the mineral, ac- 

 tually united -to the yttria. It amounts to 

 17-0065. And 



17*0065 : 45 : : 2 : 5-2Q21 = atomic weight of yttria. 



Ofyttroce. 5. There is another mineral, which was dis- 



meim 



covered by Berzelius at Finbo in Sweden, and 

 analyzed with great care, namely, the yttrocerite, 

 which he found composed as follows : 



Lime . . 50 



Yttria . . 8-1 



Protoxide of cerium 16-45 



Fluoric acid 25-45 



100-00* 



Let us suppose the lime and yttria in this min- 

 eral to be in the state of neutral fluates, and pro- 

 toxide of cerium in the state of a bifluate, and 

 let us calculate the composition, on the supposi- 

 tion that the atom of fluoric acid is 1 *25, which 

 will be proved in a subsequent chapter. 



(1.) 3-5 (atom of lime) : 1-25 (atom of fluoric acid) : : 50 

 (lime in the mineral) : 17'857 = fluoric acid united to 

 lime. 



(2.) 5-25 (atom of yttria) : 1-25 : : 8-1 : 1-928 = fluoric acid 

 united to yttria. 



(3.) 7-25 (atom of oxideof cerium) : 2-5 (2 atoms fluoric acid) 

 : : 16-45 : 5-672 = fluoric acid united to oxide of cerium. 



* Afhandlingar, IV. 151. 



