312 Chemical Composition of the Brown Lead Ore. 
photic and fluoric acids, in the last. Calcium is the radical in the Ap- 
atites, and lead in the Green Lead Ores. If we compare the results 
of the researches alluded to with those of the present analysis, we at 
once perceive in what a near relation the former stand to the latter; 
and that the Polyspharite appears to be only a Green Lead Ore, in 
which a part of the lead is replaced by lime, and a part of the chlo- 
rine by fluorine, or in which chlorine and fluorine, lead and lime are 
isomorphots with each other. Although we may in this manner ar- 
rive at a probable conclusion respecting the mode of composition in 
this mineral, and comprehend the relation of the chlorine and fluorine 
compounds to the basic salts, yet the kind of combination in the 
union of the chlorine and fluorine with calcium or with lead, remains 
to be explained. We may assume, for instance, that in the mineral 
under consideration, chlorine and_fluorine are in common united with 
lead; in which case the formula of the mineral will be, 
1 Pb: 
pe: 
EB Ca? 
or even, that the chlorine is united with the lead to form chloride of 
lead, and the fluorine with the calcium to form fluoride of calcium ; 
in which case the chemical composition of this mineral would be 
represented by the following formula : 
Pb-€l) Pb? 
3 
Caz Ca? Z 
Additional circumstances, of which I shall make mention in the 
conclusion of this memoir, particularly the circumstance that in all 
the inquiries respecting the varieties of the Brown Lead Ores, every 
one examined by me that was found to contain fluoric acid contained 
lime also, and on the other hand, those which were deficient in lime, 
were in like manner wanting in fluoric acid, serye to render the 
latter -supposition concerning the way in which the constituents of 
this mineral are united as the most probable one. If we adopt this 
formula, we can easily ascertain, by means of Berzelius’s new table 
of equivalents, the quantity of fluorine, or of phosphoric and fluoric 
acids, which the Polyspharite contains, and-which were not deter- 
Mined in the analysis. By means of a simple proportion, founded 
upon the quantities of oxide of lead and chlorine, found in the analy- 
‘Sis, we derive the proportions of cee of calcium and basic phos- 
phate of lime ; from whence 
