Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

DISTILLATION. 5

solved again in the mother liquor. By slow crystallization,

especially with a deep body of solution, large crystals are

obtained; by more rapid cooling, as by shaking the solution in a

flask under running cold water, a crystalline meal is obtained

which, because it contains less mother liquor inclosed between

the crystal layers, is purer, although of less characteristic form (dis-

turbed crystallization).

4. Suction.

Coarse crystals can be separated from the mother liquor by
sucking the mass through an ordinary funnel in which is placed

a small glass marble. If a few small crystals should run through

at first, the liquor containing them is poured a second time

through the funnel. Even fine crystals and powdery precipi-
tates can be filtered clear if a thin cord of asbestos fibers is laid

around the marble. The suction funnels of R. Hirsch and of

Buchner are also much used, for all sizes of which hardened

filters, which do not, like common filter paper, lose their fibers,
are to be obtained in the market.

If the material on the filter dissolves but slowly, it can be

washed with water, or with the liquid used for the crystallizing
medium if it is other than water; substances that dissolve more

readily may be washed with suitably diluted solvents, for example,

with mixtures of alcohol and water and finally with pure alcohol.

5. Distillation.^1

For distilling ordinary liquids, flasks are used; for substances

which solidify easily retorts are more suitable and these in the case

of high-boiling materials, may be covered with folded asbestos

paper in order to keep in the heat. The use of a condenser is

usually superfluous when distilling high-boiling substances from
retorts; in distilling low-boiling materials a condenser of suit-

able length should be joined to the distilling flask with a cork

stopper (Fig. 6), although sometimes the connection is left open;

or a short condenser may be slipped over the neck of the
distilling flask itself and made tight with corks or with pieces

of rubber tubing (Fig. 7). In the case of substances that boil

1
For fuller details regarding distillation, especially of organic liquids,
see text-books on Organic Chemical Preparations.