E. W. Balson The University
Southampton, England
Apparatus for the Study of LiquidVapor Equilibria
Among the many types of still used for the investigation of liquid-vapor equilibria are several of simple desi~nwhich are suitable for student use. such as that described by Choppin, et al. (J. CHEM. Enuc., 24, 491 (1947)) and the very simple form mentioned in "Experimental Physical Chemistry" (DANIELS,MATTHEWS, WILLIAMS,ET AL., 5th ed.. McGraw-Hill Book Co., 1956, p: 77). Another compact type of still which has been used successfully by undergraduates in the physical chemistry laboratory a t this university is described below. The apparatus is shown in the diagram, to scale, and is constructed in Pyrex glass. The liquid (ca. 50 ml) is boiled in B, and condenses on the watercooled thimble C and flows to the side vessel V by way of the funnel F, the overflow from V returning to boiler B through the U-tube U . A 0-50" or 50100" thermometer, graduated to O . l D , is fitted into the side arm as shown. In use, equilibrium is attained in 5 to 10 minutes and is indicated by constancy in composition of the condensate in V, both this composition, and that of the liquid in the boiler being determined from their respective refractive indices. Benzene-acetone, benzene-methyl alcohol, and chloroform-methyl alcohol mixtures have been employed. Despite their somewhat fragile appearance, one of the two constructed four years ago has survived; the other required repair recently. Possibly compact-
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ness has some influence on the life of the apparatus when used and stored by students.
