CYANIDES. 91- From Titanium Dioxide.
Titanium disulphide was first obtained by H. Rose (1823) on conducting
vapors of carbon disulphide over glowing titanium dioxide. The theory of
this method, which subsequently proved to be of importance for the prepa-
ration of sulphides, is the same as that of the preparation of chlorides from
oxides and carbon tetrachloride (cf. Introduction to No. 52, p. 81).
Lead a fairly strong current of hydrogen sulphide through a
wash bottle containing glycerol, a U-tube filled with calcium
chloride, a wash bottle containing carbon disulphide, and into a
piece of combustion tubing in which has been placed 4 to 5 grams
of finely-powdered titanium dioxide (No. 52). Heat the contents
of the tube to a bright red heat by means of a row burner with an
asbestos hood (Fig. 3). The vaporization of the carbon disulphide
may be hastened by placing the wash bottle in a beaker filled with
lukewarm water. Do not heat the tube until the air has been
completely expelled; during the heating revolve it a little on its
axis from time to time in order that new portions of the dioxide
may come to the surface. After about three hours the reaction
is complete; allow the preparation to cool in the current of hydro-
gen sulphide.
The titanium sulphide has the appearance of a brown powder,
but on being pressed it assumes a dark-yellow, metallic luster.
In the analysis, titanium may be determined by roasting, and
sulphur either by the method given above, or by heating the
sample in a current of oxygen and collecting the gases evolved in
ammoniacal hydrogen peroxide or in bromine water, eventually
making this solution acid and precipitating it with barium chloride.
The results show a somewhat too high titanium value, and too low
sulphur, because, when prepared in this way, the sulphide invari-
ably contains some titanium dioxide.
(d) Nitrides.
- Hydrogen Cyanide, Mercuric Cyanide, Cyanogen, and
Dithio-oxamlde.
Carbon combines with nitrogen, absorbing heat, and forms the nitride,
cyanogen:
2 C + N 2 + 7100 cal. = C 2 N 2.The endothermic nature of this substance (cf. p. 55) accounts for the
formation of cyanogen compounds in the blast furnace, and for its presence in