ANTIMONY TRICHLORIDE 309Procedure: Treat the powdered stibnite in an 8-inch dish at the
hood with the commercial hydrochloric acid; warm the mixture
slightly and keep it at 50-70°, with frequent stirring, for 20 minutes.
Finally, boil the solution for 5 minutes. Then add 15 cc. more
of concentrated hydrochloric acid; filter the solution through
asbestos felt (Note 4 (d), page 8) which has previously been
moistened with hydrochloric acid, and rinse the residue on to the
filter with an additional 15 cc. of hydrochloric acid. Evaporate
the filtrate in an open dish to 200 cc; then transfer it to a retort,
in the bottom of which are placed a few small pieces of unglazed
porcelain to prevent bumping. Place the retort on a sand bath
and distil, after first covering the bulb of the retort with an asbestos
mantle to prevent loss of heat. At first insert the neck of the
retort into a liter flask half filled with cold water (to absorb the
hydrochloric acid). When a little of the distillate begins to give
a precipitate on dropping into a tube of cold water, exchange the
receiving flask for a smaller dry one and continue the distillation
until a drop of the distillate will solidify when cooled on a watch
glass. Save the portion thus obtained for later use and continue
distilling, using a wide 6-inch test tube, which has previously been
weighed, as a receiving vessel, until all the liquid is driven out
of the retort. Stopper the test tube tightly and preserve the
preparation in it. If the product thus obtained is not white it
should be dissolved in concentrated hydrochloric acid and re-
distilled.
Note. If the stibnite contains a considerable quantity of
silicates soluble in acids, there will be left in the retort as the dis-
tillation progresses a quantity of gelatinous silicic acid which is
likely to interfere with obtaining distinct fractions of the distillate.
In such a case distil until the residue in the retort is left dry, but
without making the final change in receiving vessels. Then pour
all the distillate containing any of the antimony salt into a fresh
retort and distil again, this time separating the fractions.
Antimony Oxychloride. Pour the first portion of the distillate
saved from the above procedure into 2 liters of water. Stir, allow
to settle, and draw off the clear liquid. Stir up with water once
more, let settle, draw off as much of the water as possible, and
drain the precipitate on a suction filter. Dry it on paper towels
and put it up in a cork-stoppered test tube.