Chemical Composition of the Brown Lead Ore. 319 
One hundred parts of this mineral consist of: 
Oxide of lead, = - ~ - - 82.290 
Muriatic acid, ~ - - - - 1.989 
Phosphoric acid with a trace of oxide of iron and loss, 15.721 
ee OE 100.000 
1 atom chloride of lead = - - - 10.069 
38 atoms phosphate of lead = - - 89.931 
100.000 
The following table is arranged to facilitate a review of the re- 
sults concerning the chemical composition of the varieties of Brown 
Lead Ore herein examined. 
i = % 2 ei = 2 =r S 
Brown lead ore of e 23 23 BE BS = g s 
s |e |2°| 2° | s= |e"| * 
Sonnenwirbel 
mine. (Po- > |6.092/10.838)1.094)11.053/77.015) — |100.000 
lyspharite.) 
Mies. (amorph.) |6.444/10.642}0.248) 7.457/81.651|trace| 99.998 
| Mies: (crystal.) |5.983) 9.664/0.219| 0.848/89.268| — | 99.999 
Bleistadt. do. |7.009} 9.918/0.137| 0.771|89.174) — |100.000 
England. do. — |10.074)0.130| 0.682/89.110) — | 99.996 
Poullaouen. do. |7.048)10.090) — | — |89.910\trace|100.000 
(do. amorph.) |7.050)10.069! — | — _ /89.931\|trace|100.000 
From the researches of Mr. Wohler relating to four Phosphates 
and Arseniates of Lead it follows, as I have before remarked, that in 
the mineral Phosphates and Arseniates, a mixture in indefinite propor- 
tions, or a complete replacement of principles may happen, without 
giving rise to any variation in the crystalline form, or to the relative 
proportion of the lead in the basic salt, or to that in the chloride of 
lead. From the results of the analyses of the seven varieties of 
Brown Lead Ore, I think we can deduce the following conclusions. 
1. The Brown Lead Ores are partly combinations of one atom chlo- 
ride of lead and fluoride of calcium with three atoms and two thirds 
of phosphate of lead, and two thirds of phosphate" of lime,—partly of 
one atom chloride of lead with three atoms and two thirds phosphate 
of lead, and correspond in the first case, to the formula, 
Pb-€1 Pb?) |: 
ae P 
Caz Ca? 
PbhE1+3Pb? BP . 
in the second, to, 
