272 ELEMENTS OF GROUP" IV
Procedure: Stannous Sulphide. Place the stannous chloride in
a beaker and treat it with its own weight of water. If it dissolves
completely pour it into a large common bottle and dilute it with
1,500 cc. of hot water. If it does not all dissolve decant the solu-
tion into the bottle, crush any hard lumps with a pestle, and treat
the residue successively with small amounts of water pouring the
easily floatable suspension each time into the bottle. Make up
the volume to 1,500 cc. and, under the hood, pass hydrogen sul-
phide in through a delivery tube leading to the bottom of the bottle.
Continue this treatment until the solution is saturated with the
gas, when, after vigorous shaking, it will smell of hydrogen sul-
phide. Let the precipitate settle, decant off the clear solution
and transfer the sludge on to a gravity filter. Do not wash the
sludge; merely let it drain thoroughly. Without tearing the filter,
remove it from funnel and spread it out on paper towels on the
hot plate. Pulverize the product when it is dry.
Stannic Sulphide. Save 2 grams of stannous sulphide for an
experiment. Grind the rest together with one-half its weight
of sulphur and 0.4 its weight of ammonium chloride. Bring the
mixture into an 8-inch test tube. Close the tube with a stopper
bearing a short piece of glass tube drawn out to a capillary and
bend downward at right angles. The capillary is to relieve any
pressure caused by heating and at the same time prevent outside
air entering the tube during the heating. Lay the tube in a sand
bath pan containing a j-inch layer of sand. Then heap sand over
the part of the tube containing the charge. Heat the sand bath,
first rather moderately for 15 minutes, then for 1 hour so that the
bottom of the iron pan is bright red. Cool, break the tube, sepa-
rate the layer of stannic sulphide from the dirty-colored material
on top, pulverize the product and put it up in a 2-ounce cork-
stoppered bottle.
QUESTIONS- Experiment: Treat 0.25 gram powdered stannous sulphide
with sodium sulphide (Na 2 S) solution, warming for about 3 min-
utes. Does the solid dissolve? Then add about 0.1 gram of
powdered sulphur and warm a little longer. Does the stannous
sulphide now go into solution? Write equations and explain how
the sulphur could have caused the stannous sulphide to dissolve.
Finally acidify the solution. What is the precipitate? Equation?
Test portions of this precipitate to see if it will dissolve in