Chemical Composition of the Brown Lead Ore. 311 
These analyses yielded, in 100 parts: - 
Oxide of lead, - — - ~ ay RQ IG 
Lime, - - - - 6.47 
Muriatic acid, - - - - 2.00 
Phosphoric and fluoric acids, with loss, 19.36 
100.00 
If we observe the results of the foregoing analyses, we cannot fail 
of discovering a great resemblance between them and those obtained 
in the examination of the Phosphates and Arseniates of Lead by Mr. 
Wohler ;* while on the other hand, a remarkable difference will also be 
perceived. The Brown Lead Ore just examined, besides the custom- 
ary constituents, contains also fluoric acid and lime, neither of which 
have before been found as constituents in. the Phosphate of Lead, and 
forms therefore, a constant and fixed compound of substances, whose 
union together in minerals was before unknown. We may neverthe- 
less form a correct idea of the manner in which chlorine, fluorine, 
phosphoric acid, calcium and lead are united in this mineral, when we 
take into consideration the results of the researches of Mr. Wohler 
upon the Phosphates and Arseniates of Lead, and those of Mr. G. 
Rose upon the Apatite, which afforded us our first knowledge of the 
interchanging relations of these minerals. From the former of these, 
it follows, that the Green Lead Ores are compounds of 1 atom chlo- 
ride of lead and 32 atoms phosphate or arseniate of lead; and that 
the phosphoric and arsenic acids are so mixed in variable propor- 
tions in the compound, that they may completely replace each other, 
without giving rise to any modification in crystalline form, or to the 
relative proportion of the lead in the basic salts to that in the chlo- 
ride of lead. ‘The investigations of Mr. G. Rose concerning the 
chemical constitution of the Apatites, prove that these are isomorphous 
with the Phosphates and the Arseniates of Lead; and that one and the 
same chemical formula expresses the composition of both species, viz. 
€! P 
R +3R°< -- 
Ee As 
In this formula R stands for radical, and the Apatites differ from 
the Green Lead Ores in their chemical relations only in this respect,—. 
that chlorine and fluorine replace each other in the first, and phos- 
* Poggendorff’s Ann. d. Ph.u. Ch. Bd. IV. S. 161. 
