GREEN MANGANESE SULPHIDE. 89
solution to 2000 c.c, and treat it, at the temperature of the water
bath, with hydrogen sulphide until the precipitate settles clear.
Collect the stannous sulphide upon a large plaited filter, wash it
thoroughly with hot water, and allow it to dry over night on a
porous plate. Break up the caked product which results and
leave it in the drying closet, occasionally breaking up the lumps
and grinding them to a powder, until the mass is entirely free
from moisture.
Stannic Sulphide. Triturate the stannous sulphide, prepared
by the above directions, with half its weight of sulphur and 6 g.
of ammonium chloride. Place the mixture in an Erlenmeyer
flask, which should be about three-quarters filled, and bury the
flask to its neck on a sand bath or place it on a Babo funnel,
covering it with a cone of asbestos paper. Heat for two hours,
not too strongly, but say sufficiently to keep the iron pan of the
sand bath at a fairly bright red heat. Then, when the ammo-
nium chloride and the excess of sulphur should be completely
volatilized, allow the contents of the flask to cool. On breaking
the flask, the stannic sulphide is obtained in the form of soft,
glistening, yellow crystals. It is known in this modification
by the name of Mosaic Gold. Impurities may be removed
by decantation with water; they either float off or remain
entirely behind.
Another method for preparing this compound is to start with
stannic chloride and carry out the process as described for tita-
nium disulphide, No. 58.- Green Manganese Sulphide.
Heat a solution of 40 g. crystallized manganous sulphate in
1200 c.c. of water to boiling in a 2-liter beaker. Blow in a vigorous
current of steam, and add 300 c.c. of concentrated yellow ammo-
nium sulphide, all at one time, while the solution is being agitated by
the steam; the manganous sulphide formed appears reddish for the
first moment, immediately turns yellowish, and soon becomes dark
olive-green. Wash the precipitate, which settles well, by decan-
tation with boiling water containing a little hydrogen sulphide;
each volume of water added should be thoroughly mixed with the
precipitate by blowing in steam. All of the ammonium salt is
removed in the course of a few hours. A small amount of brown