METALLIC ANTIMONY 313from the paper and pulverize them in a mortar. Put up the prod-
uct in a cork-stoppered bottle.
QUESTIONS- Write equations for all reactions involved in the preparation
of antimony pentasulphide from stibnite.
PREPARATION 59
METALLIC ANTIMONY, Sb
This metal is obtained on a commercial scale both by reducing
antimony oxide with carbon and by reducing antimony sulphide
by means of metallic iron. The second method possesses the ad-
vantage that antimony sulphide, a natural product, is used directly
and does not need to be first converted into the oxide. The iron
sulphide formed by this method is fusible and forms an immiscible
layer which floats on top of the molten antimony. The addition
of borax facilitates the separation of the liquid layers, and thus the
globules of melted antimony are allowed to sink more easily to the
bottom of the crucible and form a metallic regulus. The upper
layer furthermore covers the surface of the metal and hinders its
oxidation and the escape of the volatile Sb2O 3.
Materials: stibnite, Sb 2 S 3 , 112 grams = 0.33 F.W.
iron filings, 48 grams,
borax, Na 2 B4O7, 30 grams.
Apparatus: clay crucible 30 grams, with cover,
gas furnace,
iron stirrer.Procedure: Mix thoroughly 112 grams of stibnite, 48 grams of
iron filings, and 30 grams of borax. Pack the mixture into a clay
crucible. Cover the crucible and heat it strongly in a gas furnace.
After half an hour remove the cover and stir gently with an iron
rod to determine if the flux is completely melted. If it is not,
replace the cover and heat for 10 minutes and again examine the
contents of the crucible. (Antimony boils at 1,380°, and pro-
longed heating diminishes the yield.) When the reaction is
complete, remove the crucible from the fumace and let it cool with
the cover on. Break the crucible with a hammer and separate the