
567Nonferrous Metals
H
2
gas, and carbon has the lowest potential. The disso-
ciation pressure of PbO is very low so that just heating
and vacuuming are not enough to reduce it back.
23.5 Roasting
After mining, crushing, grinding, and mechanical con-
centration of the ores, the rst thermal treatment is roast-
ing or sintering. Copper, lead, and zinc ores can be roasted
to reduce the amount of sulfur, antimony, and arsenic
and to reduce oxides back to metallic form. Roasting is
done in roasting furnaces. During roasting the ores and
metals are heated below melting point. Sintering of par-
ticles can occur—this process is sometimes called sinter-
ing ...