166 Description of Edwardsite. 
appearance of pure peroxide of cerium. To the acid solution ata 
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. 
Protoxide of cerium, . 25.44 or 56.53 p.c. 
Phosphoric acid, . . 12.00 “ 26.66 *“ 
a ee ere. 9") AL aay By jy A 
PERM, os tere a san, BOO r™ , 444 
MG MI... s--. 5). es SO." 338M 
44.44 98.73 
Protoxide of iron, a trace. 
Glucina, - 
Magnesia, se 
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. 
