Organic 2 Review Problem 449

Organic 2 Review Problem 449 - the Beckmann thermometer B...

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QUANTITATIVE ANALYSIS 433 available in the laboratory, it is best to use for Freezing-point determinations the following solvents, which freeze a few degrees above o°C. SOLVENT Benzene Nitrobenzene Cyclohexane Bromoform i ,2-Dibromoethane FREEZING-POINT 5'5 7-8 8-0 MOLECULAR DEPRESSION CONSTANT (K) So 69 201 I 44 118 Water 18-6 Acetic acid 17 39-0 Certain practical points concerning the use of these solvents are dis- cussed after the description of the experimental method: water and acetic acid are also included, although the former is rarely used in organic work, and the latter presents certain experimental difficulties which are also discussed later. The apparatus (Fig. 79) used consists of a glass tube T (usually about 18 cm. in length and 2-5-3-0 cms. in diameter), having a short side-arm A, as shown. Into the top of T are fitted through a cork
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Unformatted text preview: the Beckmann thermometer B (already "set" for the required solvent) and the stirrer S made of thin glass rod. It is advisable for the hole in the cork carrying the stirrer S to be protected by a short collar C of glass tubing, the handle of the stirrer being bent after threading through the collar. The tube T fits into an outer tube J, which acts as an air-jacket to prevent too rapid cooling of the contents of T. J in turn is held in a metal Hd covering a large glass jar of ice-water: a much heavier and stronger stirrer D passes through this lid to enable the ice-water mixture to be thoroughly stirred from time to time. FIO. 79. Weigh the clean dry tube T, then add about 25 ml. of the pure solvent (i.e., sufficient to ensure that the bulb of the thermometer...
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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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