appropriate capillary is joined to (e) so that it and the wide tube (c) end in the same horizontal plane. The open manometer consists of a U-shaped tube of '/TI mm. internal diameter F'yrex tubing, which is connected to the aspirator and bubbler. As a cathetometer is often not available in the laboratory a simple and efficientsubstitute can be constructed by mounting a vernier caliper on small metal blocks in such fashion that the knife edges used for measuring internal diameter come directly over the manometer tnbe. The height of the meniscus can then be measured directly to 0.01 cm., with further estimation possible. The mercury aspirator recommended by Sugden is constructed by drawing out the tube of a 250-ml. separatory funnel to a fine capillary, the diameter of which should he such as to cause bubbles to form a t the rate of one per second on the bubbler tuhes. The manometer, caliper, and aspirator are mounted on a wooden support, with the glass tubing supported by wires passing through holes in the support. The bubbler is placed in the laboratory constant temperature bath, or, if measurements a t more than one temperature are desired, a simple temperature bath with control to a t least O.l°C. can be constructed from a double-walled container, such as an old calorimeter tank, with a motor stirrer mounted on a separate support to reduce vibration. An immersion heater and a light bulb are operated manually and serve to heat and control the temperature. A 10O0C. X '/la thermometer is used. An excellent extension rod for mounting the bubbler or thermometer can be made by screwing a tripod leg into the socket left when the adjustable portion and jaws of a single buret clamp are removed. The instrument constant, A, is determined by measurement of pure, fractionated benzene, the surface tension of which is given by the equation
and substitution of the suitable values in equation (1).
The density of benzene a t various temperatures can be found in the Critical Tables (4). The density of the manometer alcohol, which is tinted with fuchsine, is determined a t a few temperatures between 20' and 30°C. and a graph or table constructed for intermediate temperatures. The pressure diierence in cm. of alcobol is converted to dynes/sq. an. As bubbles are formed on the large tube, the stopcock of which is open, there is an increase in pressure and then a sudden decrease as the bubble bursts. The reading is taken a t the lowest pressure, after which the stopcock is closed and the pressure of the bubbles formed on the small tnbe taken. The density-temperature equation for various liquids to he tested can usually be found in the literature or can be determined for a range of temperature as a subsidiary experiment. The parachor of the compound can be determined after measurement and compared with known values, and the critical temperature and the constant can be calculated from data a t two different temperatures by means of the Ramsay and Shields' modification (7) of the Eotvos equation (3). Benzonitrile, methyl ethyl ketone, benzyl alcohol, butyl chloroacetate, ethyleneglycol monoethyl ether, and nz-iodotoluene were measured with the apparatus as described. The following liquids are recommended for original work on the part of the student: anisaldehyde, chloroacetone, o-dichlorobenzene, a-naphthyl isocyanate, &rt.-bntyl bromide, ethylaniline, eugenol, heptaldehyde, isopropyl bromide, n-propyl iodide, npropyl n-proprionate, o-chlorophenol, m-chloroaniline, p-cymene, o-iodotoluene, o-iodoanisole, methyl ptoluene sulfonate, and terpineol. As an example of the determinations possible, the measurement of benzyl alcobol may be considered. From 25-35T. the values of the surface tension give the approximate equation, ST = 44.593 - 0.126%; a parachor of 263.3 as compared with the known value of 266.1; a critical temperature of 455OC.; and a constant, k, of 2.15.
LITERATURE CITED
(1)
ADAH, "The
physics and chemistry of surfaces," pp. 12-8, 292424, Clarendon Press. Oxford, 1930. CANTOR, Wied. Ann., 47, 399 (1892). ELirvos, ibid., 27, 448 (1886). Intarnotionel Critical Tables, 3. 28.
5) JAEGER, A k d . Wiss. Wicn, 100, I I A , 215, 493 (1891). 6) JAE~GER, Z. onorg. C h . , 101, 1 (1917). 7) RAMSAY AND SHIELDS, Z. p h y ~ k Chem., . 12,431 (1893). 8) SUDDEN, J . , C h . Soc., 121, 858 (1922). 9) SUGDEN, ~ b t d . .125, 27 (1925).
DEMONSTRATION EXPERIMENTS USING UNIVERSAL INDICATORSA CORRECTION Two minor errors appear in this article, J. C ~ M .of hmmothymol blue should he 50 mg. instead of 60 mg. On page 276, C h .Abstr., 23,2120 (1929) should rials for Yamada's Indicator," on page 275, the amount be added to Reference 2.
Enuc., 14, 274-6 (June, 1937). In the table, "Mate-
