MERCURY FROM CINNABAR. 25DESULPHURIZATION OF SULPHIDES BY THE PRE-
CIPITATION PROCESS.
- Antimony from Stibnite.
Sulphides containing lead and antimony are frequently treated metallur-
gically by the so-called "Precipitation Process." By this is understood the
fusion of the ore with iron and suitable substances to form a slag, whereby
the iron serves as a desulphurizing agent. The sulphide of iron formed dis-
solves in the slag, and the precipitated metals collect at the bottom of the
furnace.
Place a mixture of 100 g. powdered stibnite, 42 g. iron filings,
10 g. anhydrous sodium sulphate, and 2 g. wood-charcoal powder
in a Hessian crucible and heat in a charcoal furnace. The tem-
perature should not rise high enough to melt the iron sulphide
slag completely, but just sufficiently to soften it; this point is
determined by stirring the fusion with an iron rod. After cool-
ing and breaking the crucible a fused mass of antimony, weigh-
ing about 65 g., is found at the bottom. Test a sample of this
crude antimony qualitatively for the presence of arsenic, copper,
iron, and lead.
Purification I. Mix the finely-powdered, crude antimony with
one-fourth its weight of powdered stibnite and an equal amount of
anhydrous sodium carbonate, and melt over the blast lamp in a por-
celain crucible surrounded with a clay mantle. Yield, 60 to 65 g.
Purification II. To remove arsenic from the antimony puri-
fied according to I, pulverize the metal again, mix it with 4 g.sodium carbonate and 0.2 g. potassium nitrate, and melt the
mixture in the manner just described. Yield, 50 to 55 g. of pure
antimony. Dependent experiment, No. 88.
- Mercury from Cinnabar; Sodium and Ammonium
Amalgams.
Heat a mixture of 23 g. cinnabar and somewhat more than the
calculated amount of iron filings in a small retort of difncultly-
fusible glass. The mercury distils into a small flask which serves
as receiver. Yield, 16 to 18 g.
Sodium Amalgam. Pour the mercury so obtained into a test
tube and add clean, freshly cut pieces of sodium, about the size
of grains of wheat, waiting each time before adding a fresh piece
until the previous one has reacted; toward the end assist the