Organic 2 Review Problem 42

Organic 2 Review - 26 PRACTICAL ORGANIC CHEMISTRY in Fig U(B is probably the most efficient and generally u seful type available in most

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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 (A) 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 p1G u 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.

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