Page 8 - A HANDBOOK OF ORGANIC ANALYSIS QUALITATIVE AND QUANTITATIVE

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PRELIMINARY INVESTIGATION 3
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heated in a test-tube, but under the ' vacuum' afforded by
a filter-pump. Conditions being suitable, the entire quantity
may be fractionated as before, except that the receiver now
consists of a small distilling-flask attached to the filter-pump
by means of pressure-tubing, a manometer being placed be-
tween the receiver and the -pump. In order to obviate
• bumping'it is advisable to lead into the liquid a fine capillary
tube admitting a very slow current of air, or to place in the
liquid a few pieces of porous earthenware. All stoppers should
be of indiarubber, and it is well to replace the usual form of
distilling flask by one having a double neck, as recommended
by Claisen (Fig. a).

FIG. 2.
In the case of solids, a little of the original substance is
finely powdered, pressed out upon a porous plate or upon
several thicknesses of hardened filter-paper, dried thoroughly
in air at about 40° or in a desiccator, and submitted to melt-
ing-point determination. A small quantity of the sample is
forced into the open end of a thin-walled glass capillary tube
6-8cm. long and sealed at one end ; it is then shaken down
to the closed end by repeatedly dropping the capillary tube
on to a hard surface through a vertical glass tube 6-8 mm. in
diameter and 4o-6o cm. long. The fine tube is then attached