82 HALOGEN COMPOUNDS.
accomplished by means of charcoal, but the oxides of carbon, on the other
hand, can be reduced by aluminium; an equilibrium mixture of aluminium
oxide, aluminium, carbon, and oxides of carbon, therefore, can contain only
an infinitesimal amount of aluminium. If, however, this minute amount of
aluminium in the mixture is removed continuously by causing it to combine
with chlorine, an opportunity is thus afforded for a continuous reproduction
of fresh quantities of aluminium from the reduction of its oxide, until the entire
amount of the latter is exhausted.
The preparation of titanium tetrachloride from rutile is the most con-
venient laboratory method for obtaining pure titanium compounds from that
inexpensive mineral. Instead of using carbon and chlorine separately, vapors
of carbon tetrachloride may be conducted over the heated oxide; the same
end may be attained by using sulphur chloride.
Mix 100 g. of finely powdered rutile intimately with 40 g. of
lampblack, and knead the mixture, with the aid of as little starch
paste as possible, into a thick, although still plastic mass. Shape
the mass into pellets of about 0.5 cm. diameter, and dry them
first in the hot closet, and then in a crucible placed in the
charcoal furnace. Introduce the dry and very brittle pellets
carefully into a wide combustion tube, and arrange the appa-
ratus, which must be carefully dried, as shown in the sketch
below (Fig. 16). Rubber connectors are to be avoided as muchCombustion FurnacePIG. 16.as possible. Before beginning the chlorination ignite the pellets
again, this time in an atmosphere of carbon dioxide, in order to
remove the last traces of moisture; and meanwhile start the evo-
lution of chlorine in the generator. Then connect the apparatus
for the first time with the receiver (capacity 200 to 300 c.c),
which is surrounded by ice. Conduct chlorine into the appa-
ratus, and heat the tube, which rests in a combustion furnace, at
first with small flames, then gradually bring it to a red heat. It