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Unformatted text preview: 26 PRACTICAL ORGANIC CHEMISTRY in Fig. U(B) is probably the most efficient and generally u seful
type available in most laboratories. It consists of a simple glass
column, packed with very short sections of glass tubing, the bore
of these sections preferably decreasing steadily up the c olumn.
For general purposes, the column itself should be about 11-12 mm.
internal diameter, and the glass sections* towards the bottom of
the column should be about 5 mm. long and 6 mm. external
diameter, and towards the top about 3 mm. long and 5 mm,
diameter: the length of the column actually packed with the
tubes should be about 20 cm., but for low-boiling mixtures this
length of the c olumn may be considerably increased, and for highboiling mixtures correspondingly decreased. To retain the glass
tubes in p osition, it is i nadvisable to constrict the column immediately below the tube, as t his readily causes " choking" of the
column w hen in use. It is b etter either to seal across the inside
of the c olumn a v ery fine glass rod, on w hich the tubes may rest,
or (more easily) to have one section of glass tubing rather larger
than the rest at the b ottom of the c olumn and to fix this permanently in place by f using it
carefully to the wall of the
column. The sections must be
arranged as irregularly as possible in the c olumn: if they
tend to arrange themselves
regularly they should be well
shaken up, otherwise " channelling " of the condensed
liquid will occur and the efficiency of the column will be decreased. These sections of
glass tubing are preferable to
similar sections of metal for
two reasons, (a) the metal sections, because of their low
specific heat, do not condense
sufficient of the ascending
vapour, and the efficiency of
the c olumn falls considerably
in consequence; (b) if the t ube
becomes fouled in use, particularly by traces of t arry pro* These g lass s ections f or f ractionating c olumns m ay he p urchased f rom
Messrs. Q uickfit & Q uartz, L td., Q uickfit W orks, S tone,"Staffs, S Tl5 O BG. ...
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.
- Fall '06
- Organic chemistry