imes decrepitates and
yields a sublimate of sulphur. Before the Bp. on Ch. easily reduced to
the metallic state, the Ch. becoming coated with sulphate and oxide of
lead. The metallic globule usually contains a little silver. To separate
this, the process known as "cupellation" is employed. A hole is bored
into the Ch. about 1 cm. in diameter and about 6 mm. deep. Into this
hole is placed a stiff paste made by mixing finely pulverized bone-ash
with a little soda and water. This paste is pressed in hard, and then
the surface is smoothed off, and the centre is slightly depressed with
the rounded end of a glass rod. The charcoal so prepared is set in a
warm place to allow the paste to dry. When the paste is quite dry the
small globule of lead is placed in the depression in the centre of the
bone-ash "cupel," and is there exposed to the O. F. from the Bp. The
lead is oxidized and is absorbed by the bone-ash, while any silver
present will remain in the central depression as a bright shining bead.

~Cerusite~, PbCO_{3}, PbO . 84, CO_{2} . 16.--H = 3.0-3.5, G = 6.46-6.57.
Color, white, gray, or yellow. Lustre, adamantine. Crystallizes in
prismatic needles. When heated in an ignition tube carbon dioxide is
evolved and the residue turns yellow. Before the Bp. on Ch. readily
reduced to metallic lead.

~Anglesite~, PbSO_{4}, PbO . 74, SO_{3} . 26.--H = 2.0-3.0, G = 6.12-6.39.
Color, yellow, gray, and brown. Lustre, adamantine, resinous. Heated in
an ignition tube decrepitates, and sometimes yields a little water.
Before the Bp. on Ch. fuses to a clear bead, which on cooling becomes
opaque. Before the Bp. on Ch. with Na_{2}CO_{3} is reduced to the metal
giving a yellow coating. The Na_{2}CO_{3} absorbed by the coal reacts
for S.

ORES OF MANGANESE

~Pyrolusite~, MnO_{2}, Mn . 63.2, O . 36.8.--H = 2.0-2.5, G = 4.82. Color,
iron-black to steel-gray. Lustre, non-metallic. Heated in an ignition
tube yields generally a little water, and if the temperature be high
enough, oxygen is evolved. Before the Bp. on Ch. infusible. In borax
bead gives characteristic color.

~Psilomelane~, Mn_{2}O_{3} + H_{2}O.--

H = 5.5-6.0, G = 3.7-4.7.

Color, iron-black to steel-gray. Generally resembles pyrolusite, but is
distinguished from it by its superior hardness. It frequently contains
BaO and Li_{2}O. It behaves before the Bp. like pyrolusite.

~Wad~ (Bog Manganese).--This mineral is essentially MnO_{2}, MnO, and
H_{2}O, with sm