Chemical Composition of the Brown Lead Ore. 315 
about one third of an inch in Jength and two lines in diameter, and 
of a clove-brown color. ‘They were feebly translucent, and exhibi- 
ted upon their sides perpendicular to the axis (R—© ), a drusy sur- 
face. The true specific gravity of this mineral was 6.983. Pulver- 
ized and heated with sulphuric acid in a platina capsule, it occasion- 
ed a strong corrosion on a glass plate. Its behavior before the blow- 
pipe was similar to that of the preceding variety. One hundred 
parts of the mineral contained, 
Oxide of lead, - - - - 81.330 
Muriatic acid, - - - 1.909 
ae ee E is - 0.430 
Phosphoric and fluoric acids, with loss, 16.331 
- 100.000 
. If we estimate these numbers agreeably to the formula employed 
above, taking as the basis of calculation the quantities of chlorine and 
oxide of lead found in the mineral, the crystallized Brown Lead Ore 
of Mies will consist of, 
Chloride of lead, - - - 9.664 
Fluoride of calcium, - = REE, 0.219 
Basic phosphate of lead, - - 89.263 
lime, - - 0.848 
99.999. 
4. Crystallized Brown Lead Ore of Bleistadt.—This constitutes, 
as is well known, the most beautiful of the crystallized Brown Lead 
Ores, and occurs in perfectly transparent prisms of a clove-brown color. 
Prof. Breithaupt had the kindness to furnish me with very beautiful 
erystals for this examination. The specific gravity of this variety is 
7.009. Before the blowpipe it decrepitates at first, but afterwards 
melts. The globule crystallizes during congelation. Melted with 
carbonate of soda it affords metallic lead, but offers no indications of 
arsenic. Heated with sulphuric acid, it corrodes glass. The solu- 
tion of the mineral freed from lead by means of sulphuretted hydro- 
gen, affords a precipitate on the addition of oxalate of potash, or of 
sulphuric acid diluted with alcohol. By a long continued stream of 
sulphuretted hydrogen, only a slight precipitate of sulphur appeared. 
One hundred parts of the mineral were-composed: of, 
