C, Alumina, - 4.333 - - 
D. Lime, = 28.000. ~ + a= 
97.999 
100.000 
ie | a 
ow Arr. XXV. csSRentatdd on the common methods of detect. 
ing Cobalt. By. Prof. J. F. Dana, of Dartmouth Col. 
lege. 
[The following letter was addressed by Prof. Dana to 
the Editor, in consequence of doubts expressed by the 
latter, as to the genuineness of some specimens of arsenical 
cobalt, whose locality was announced in the last number 
of this Journal. It is but fair to say, that those doubts are 
now removed, so far, at least, as the question of the emist- 
ence of cobalt in this ore is concerned.—Ed d.) 
ee 
a) 
or 
Dartmouth College, Hanover, 
. H. June 19th, 1824. 
[To the Editor.) 
Dear Sir, 
ely gives me much pleasure to acknowledge the ou of 
Your favour of the 15th instant; Tam happy to hear that 
you received the ‘ Arsenical "Cobalt, ”? and piu 
happy to learn that your health permits you to m 
€xperiments. I had made some preliminary Bi perinvents 
On the ore of which you now have a specimen, and intend 
a full analysis of it as soon as I can satisfy myself of any 
ood method of separating arsenic, cobalt and iron, perfect- 
: from each other—three metals, each of which adheres 
re with the most obstinate pertinacity. The Fran- 
@ ore contains these three metals, and also gives indica- 
tions of sulphur. lam aware — Arsentcal Cobalt is lia- 
to the ot 
alee 
