SODIUM SULPHANTIMONATE 311Sodium sulphantimonate can be prepared from stibnite by the
combined action of a solution of sodium sulphide and sulphur,
2S + Sb 2 S 3 -»• Sb 2 S 6
3Na 2 S + Sb 2 S 6 -»• 2Na 3 SbS 4
it crystallizes well with nine molecules of water.
The hydrolysis of this salt, which produces a dirty appearing
reddish brown precipitate consisting of an indefinite mixture of
Sb 2 S 6 and Sb 2 O 6 , may be prevented by an excess of sodium sul-
phide or by the presence of sodium hydroxide.
Materials: powdered stibnite, Sb 2 S 3 , 67 grams = 0.2 F.W.
sodium sulphide, Na 2 S-9H 2 O, 140 grams, or use
47 grams of anhydrous sodium sulphide and an
additional 93 cc. of water,
powdered sulphur, 13 grams.
Apparatus: 750-cc. casserole.
suction filter and trap bottle.
8-inch crystallizing dish with glass plate.
iron ring and ring stand.
Bunsen burner.
Procedure: To the finely powdered stibnite, sodium sulphide,
and powdered sulphur in a casserole add 150 cc. of water, bring to
a boil, and keep at the boiling temperature for 15 minutes. Filter
with suction and rinse the residue in the dish and on the filter with
hot water containing a little NaOH, bringing up the volume of the
solution to 250 cc. While still hot put it away in a covered dish,
with a towel placed over it, to crystallize. Drain the crystals;
evaporate the mother liquor somewhat to obtain a second crop of
crystals. If there is any tendency for a muddy brownish precipi-
tate to form in the solution, or for the same substance to form as
a scum on the crystals, add a little 6 N NaOH to the solution and
rinse the crystals in it. Spread the crystals on paper towels, and
as soon as they are dry, stopper them tightly in an 8-ounce cork-
stoppered bottle.
QUESTIONS- What is the acid of which Na 3 SbS 4 is the salt? Add HC1 to
a solution of this salt. Is the acid set free? Is it a stable acid? - What is the primary reaction in the hydrolysis of Na 3 SbS4?