Chemical Composition ¢ the Brown Lead Ore. 309 
Phosphate of iron and. métillic lead were obtained, with boracic 
acid and iron. The mineral was completely dissolved at an ordinary 
temperature in nitric acid, unattended with effervescence and without 
leaving any residue behind. The solution formed a colorless liquid, 
from which, in the cold, were deposited after the nitrate of lead, the 
chloride of lead in long needle-like crystals. The decanted solution 
exhibited the following properties. 
Nitrate of silver gave a dense precipitate of chloride of silver. 
A stream of sulphuretted hydrogen produced a dense brown pre- 
cipitate, which farther enquiry showed to consist wholly of sulphuret 
of lead. By continuing the passage of this gas for a ae time, a 
slightly yellowish precipitate of sulphur made its appearance. 
Hydro-sulphuret of ammonia threw down from the ile which 
had been completely freed from lead by sulphuretted hydrogen, a 
white precipitate, which I at first took for alumine, as indications of 
this base had been noticed in experiments with the blowpipe. A 
closer examination, however, proved that this precipitate consisted 
of a phosphate of lime with excess of base. In order fully to de- 
termine the presence or absence of alumine, I fused together, after 
the method of Berzelius, two parts of the mineral. with six of car- 
bonate of soda and one and a half of silica, and dissolved the result- 
ing mass in water. The insoluble portion being treated with muri- 
atic acid, the silica separated as usual, and the filtered liquid tested 
for alumine, no trace of this base was afforded ; but on the contrary, 
it was found to contain lime. From the solution of the mineral 
wholly freed from lead by sulphuretted hydrogen, sulphuric acid 
threw down a voluminous precipitate, which was partly dissolved in 
a large excess of water; which solution was much troubled by the 
addition of oxalate of potash. The solution, after the precipitation 
of the lime, being mingled with alcohol for the complete se 
of the sulphate of lime, was found to contain no additional bases. 
Nitrate of silver produced in it a yellow precipitate, soluble in caustic 
ammonia and nitric acid. 
For the purpose of ascertaining whether fluoric acid was an ingre- 
dient in this mineral, one gramme of it was heated with sulphuric 
acid in a platina capsule. A glass plate held over it, manifested 
after the experiment, a distinct corrosion. ‘This striking appearance 
induced me to repeat the experiment for a number of times, which 
was always attended with the same result; and the presence of fluoric 
Vor. XXII.—No. 2. 40 
