ISDCSTRIL4L A N D ENGISEERING CHEiIfISTRY
November, 1925
1201
VAPOR
COMPOJtTtON
1
/
/
PO 20 ~
I
0 that consistent and correct results could be obtained only when the liquid distilled smoothly and without "bumping." When bumping occurred the distillate approached in composition the liquid from which i t was derived. Observation showed that this was not due to the carrying over of liquid mechanically. Apparently, when bumping occurs the superheated liquid in contact with the bottom of the flask vaporizes almost completely and the vapor bubbles rise so quickly that equilibrium between vapor and liquid is not attained. In the accompanying graphs for the vapor composition relationships in the systems phenol-o-cresol, phenol-m-cresol and phenol-p-cresol, the curves are not drawn directly from the experimental data, but represent the vapor composition relationships which would obtain if these various pairs of liquids were "ideal" liquid mixtures. In such ideal mixtures the composition of the distillate from any given mixture can be calculated from the equation APo A P G $. BPb w h e r e X is the fraction by weight of the component a in the distillate A is. the fraction by weight of the component a in the liquid from which the distillate is obtained B is the fraction by weight of the component b in the liquid from which the distillate is obtained P, and Pb are the vapor pressures of pure a and pure b,
X =
20
PO
60
80
100
respectively, a t the temperature corresponding t o the boiling point of the liquid A B under the pressure used
The data used in the calculation of these ideal relationships are those of Kahlbaum.' Since the Tapor pressures of mcresol and p-cresol a t the same temperature are so nearly identical, one curve may be used to represent the ideal relationships in both the system phenol-m-cresol and the system phenol-p-cresol. Points corresponding to the experimentally determined results are also shown on these same graphs. It will be observed that in every case the agreement between the theoretical and the actual results is so close that we are justified in concluding that phenol forms ideal liquid mixtures with each of the three cresols. A few determinations made under reduced pressure also showed excellent agreement between the theoretical and the calculated values. It was not considered necessary, however, t o obtain complete data a t the lower pressures. The data presented in this article supply the information necessary for the calculation of the theoretical minimum reflux ratio and the minimum number of sections required in the fractionating columns of stills for the separation of phenol from water and from cresol. 7
Z p h y s i k Chem , a6, 603 (1898)
Uses for a Broken Electric Light Bulb' By Ralph F. Tefft and D. J. Brown UNIVERSITY OF
NEBRASKA, LINCOLN, NZBR.
convenient substitute for short platinum wires for A connections through glass may be found in almost any nitrogen-filled light. The two wires that conduct the current through the glass of the bulb to the light filament are easily seaIed into glass. The best method is to fuse a bead of the glass from the same part of the bulb onto the wire and then to avoid too high a temperature. A safety regulator was placed in series with the heating unit on a 110-volt circuit t o avoid excessive overheating due to failure of the ordinary magnetic control. Under the conditions due to the frequent make and break of the current the wires showed less tendency t o crack the glass than platinum. 1 Received
July 29, 1925.
These wires seem very resistant. After being in contact with mercury for several months they showed no signs of amalgamation. They have been used to make contact through glass for mercurous sulfate and calomel electrodes. The contact must be covered with mercury before the addition of the mercury salt mixture. The wire had no effect on the potential of the electrodes. When it was used as a contact at the make and break of current for a thermoregulator, it was not corroded. These wires can be sealed into ordinary glass and used as substitutes for platinum in the flame tests which are used so frequently in elementary qualitative analysis. They seem more resistant to the condition. met there than platinum. The wire cannot be used for bead tests.
