166 Description of Edwardsite. 



appearance of pure peroxide of cerium. To the acid solution at a 

 boiling temperature, sulphate of potassa was added, and immediately 

 afterwards a little ammonia, but not sufficient to supersaturate the 

 free acid. A fine white grained precipitate instantly appeared, which 

 was taken for subsulphate of zirconia. It was separated, re-dis- 

 solved, and precipitated by potassa. The solution from which the 

 subsulphate was separated was then thrown down by potassa, and the 

 precipitate after edulcoration and ignition weighed 8 centigrammes. 

 It possessed moreover the properties of pure peroxide of cerium. 

 We have therefore 11.5 centigrammes peroxide of cerium in the 

 15 centigrammes, leaving 3.5 centigrammes for the zirconia : and 

 regarding the undissolved reddish brown matter E as peroxide of 

 cerium, which it closely resembled after ignition, the total weight of 

 this oxide from 45 centigrammes of the mineral is 27.4 centigrammes, 

 or 24.53 centigrammes of the protoxide, in which state of oxidation 

 the cerium no doubt exists in the mineral. 



The following, therefore, is a summary of the results obtained in 

 this analysis. 



Centigrammes. 



c. 



The phosphoric acid and oxide of cerium are almost exactly in 

 the ratio of one atom of the former to one and a half of the latter. 

 The Edwardsite is therefore a basic sesquiphosphate of the protoxide 

 of cerium. In what manner the other ingredients are combined, or 

 whether they are merely accidental, I shall not venture to decide 

 without an opportunity of confirming the proportions here stated by 

 a repetition of the analysis on a larger quantity of the mineral. 



Charleston, S. C. January 30th, 1837. 



