330 EARTHS PROPER. 



that is to say, had the acid been 0'093 more, 

 then the atomic weight of yttria would have been 



of hydrate 3. Klaproth found that yttria precipitated from 

 muriatic acid, and dried in the open air after 

 being well washed, was a hydrate composed of 



Yttria ... 69 



Water . . . 31 



100 



For 100 parts of it when heated to redness lost 

 31 parts of its weight. Now, 31 : 69 : : 2*25 : 

 5*008 = atomic weight of yttria, supposing the 

 hydrate to contain just 2 atoms water. 



Thus we have got three atomic weights of 

 yttria. 



(1.) From the carbonate . . 5-285 

 (2.) From the sulphate . 5-4012 



(3.) From the hydrate . . 5-008 



3 ) 15-6942 

 Mean .... 5-2314 



This mean must be very near the truth : we 

 may, therefore, adopt 5*%5 as the true atomic 

 weight of yttria in order to make that weight 

 accord with Dr. Prout's law. 

 Analysis of 4. Gadolinite, the mineral in which yttria was 



gadolinite. 



first discovered, has been likewise analyzed with 



