90 SULPHIDES.
manganese oxide is formed during the process, by oxidation of
the sulphide, but it floats on top of the liquid and is removed by
the decantation.
Finally dry the manganous sulphide mud by draining it rapidly
on a large suction filter, wash it with alcohol and dry it in a desic-
cator over sulphuric acid.
The preparation of green manganese sulphide does not always
succeed the first time.- Titanium Disulphide.
- From Titanium Tetrachloride.
This preparation furnishes an example of the decomposition of a chloride
by hydrogen sulphide in the absence of water (cf. p. 68).
The apparatus described in No. 53 is used (Fig. 17, p. 84),
but instead of hydrogen, hydrogen sulphide is employed. It is
first passed through a small wash-b.ottle containing glycerol, in
order that the bubbles may be counted, and through two U-tubes
containing calcium chloride to dry the gas. In the retort 50 g.of titanium chloride are placed.
First of all pass a rapid stream of hydrogen sulphide through
the apparatus and heat the combustion tube to dark redness; then
heat the titanium chloride in the retort nearly to boiling, and keep
it at that point by means of a small flame. The vapors of titanium
tetrachloride charged with hydrogen sulphide are decomposed in
the hot tube to TiS 2 and HC1; any unchanged titanium chloride
that collects in the receiver is returned to the retort, again distilled,
and the process repeated even a third time. The inlet tube for
the hydrogen sulphide must not be too narrow, or it may become
stopped with titanium disulphide formed within the retort. When
all of the titanium tetrachloride has reacted, withdraw the retort,
and, in order to remove all traces of tetrachloride from the product,
pass a current of hydrogen or of carbon dioxide through the tube.
After allowing the tube to cool, remove its contents in the manner
described in No. 53. A product is obtained which consists of about
10 g. of dark brass-yellow leaflets similar to those of Mosaic gold.
Analyze one sample for titanium by roasting it in a porcelaincrucible and weighing it as TiO 2 ; a second portion for sulphur by
taking it up in aqua regia (or in the manner described below) and
precipitating the highly diluted solution with barium chloride.