Organic 2 Review Problem 76

Organic 2 Review Problem 76 - capillary tube so that the...

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6o PRACTICAL ORGANIC CHEMISTRY convenient. For separations on a smaller scale a dropping-pipette should be used: for the removal of an upper layer, the bent pipette (Fig. 31) is recommended. An ordinary hand centrifuge may be employed to promote a clean line of demarcation between two im- miscible liquids which show a tendency to emulsify. 7-5 cm. 7-5 cm. V FIG. 29. FIG. 30. FIG. 31. In order to minimise the absorption of liquids by corks, single pieces of apparatus are used wherever possible. A skilled worker can use a micro-Bunsen burner for most types of heating. Nevertheless, as there is a tendency for a liquid to shoot out of a small test-tube when heated, it is preferable to place the tube in a hot water-bath or in a metal heating block. A small glycerol bath is suitable for distillations and heating under reflux, the glycerol being subsequently easily removed from flasks, etc., by washing with water. Determination of Boiling-points. The following alternative methods are recommended, (a) Draw one drop of the liquid into a
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Unformatted text preview: capillary tube so that the drop is about i cm. from one end. Hold the tube horizontally and quickly seal this end in a micro-burner. Attach the tube (with the open end upwards) to a thermometer in the melting-point apparatus (Fig. i(c), p. 3) so that the trapped bubble of air in the capillary tube is below the surface of the bath-liquid. Now heat the bath, and take as the b.p. of the liquid that temperature at which the upper level of the bubble reaches the level of the surface of the bath liquid, (b) Prepare a fairly wide capillary tube A (ca. 4 mm. X 8 cm.) (Fig. 32). Using a fine pipette insert about i cm. length of the liquid into the bottom of the tube. Now place in the tube A a fine inverted melting-point tube B of about i mm. diameter, sealed at the upper end. Fasten the capillary tube to the ther- FIG. 32. mometer by means of a rubber band and place in a melting-point apparatus. Heat slowly until a stream of bubbles rises from the bottom...
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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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