Organic 2 Review Problem 81

Organic 2 Review Problem 81 - METHODS AND M ANIPULATION 65...

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Unformatted text preview: METHODS AND M ANIPULATION 65 Distillation under reduced pressure. The student should first read details of this operation on a macro-scale (p. 28). For micro-scale work the apparatus shown in Fig. 40 is very convenient. A small pear- FIG. 41(D). shaped flask of 5 ml. capacity is fitted w ith a small side-tube through which a piece of glass tubing can be passed. The latter is held in position by a r ubber b ung,* and is drawn out into a fine capillary tube to act as an air-leak. The upper end of the tubing is fitted with pressure tubing and a screw-clip to regulate the flow of air. Distilling flasks of alternative design are shown in Figs. 4 i(A) and 41(6). With a single receiver tube as shown in Fig. 40 it is necessary to interrupt the distillation each time the receiver is changed. For more precise work a multiple receiver as shown in Fig. 42 should be used. The lower part L of this apparatus contains 6 small collecting tubes C, eachf supported in a wire hoop attached to a fixed vertical glass rod. The receptacle L is attached to the upper part of the apparatus by a ground-in glass j oint, J, carefully l ubricated by silicone grease. By gently rotating the receptacle L about the ground-glass joint J, it is possible to collect the d ifferent fractions in the separate tubes without stopping the distillation, and hence without alteration of pressure. * The type of a pparatus shown in Fig. 40 can be obtained with ground-in glass joints thus obviating FIG. 42. the use of rubber bungs. f Each t ube C s hould have an i dentification m ark, so t hat the b .p./pressure of the c ontents of each can be recorded d uring the d istillation. ...
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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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