Gilbert F. Pollnow University of Wisconsin oshkosh. Wisconsin 54901
Binary Liquid-Vapor Boiling Point Diagrams on a Graphic Desk Top Computer
An interactive graphic computer program written in Basic for the Tetronix 4051 is now available from the author for computing the liquid and vapor composition curves as n funcriun of temperature for any volatile twocomponent system. nroeram d o t s hoth the ideal and Van Lam reore~ - - - The - ~ sentations for the system along with the experimental boiling m i n t cornnosition data as shown in Fieure 1. The ooints are plotted asgenerated to emphasize the iiscrete andconjugate nature of the experimental and theoretical d a t a The program computes the Van Laar constants using the method described in Daniels' which reauires the composition and boiling point of the azeotrope, barometric pressure, and the ~ n t o i nGapor i pressure constants for hoth pure components. Tabular output of the liquid and vapor compositions as a function of temperature together with the Van Laar constants and all the input parameters in a self-evident format is optional as shown in Figure 2. A ~ ' ~ Wphysical O chemistrv rtudents are required to calculate the Van l.aar constants and the conjugate comp~sitiona corresponding to one of the rahular output points on their personal mlculators for a known system inorder to reinforce thrir understanding of the rumputations prior to performing the laboratory experiment as described in U n n i e l ~In . ~addition, the Van Lnar amstants are also determined hy the srudents using the lenst squares method of Wingard er al."and artemnts are mnde to ratiunalire the differences. This experiment also provides an excellent opportunity to demonstrate the use of a soft-ware polynomial regression program for plotting and fitting their refractive index composition data and then using the resulting polynomial to compute the conL~
jugate compositions from their measured refractive indices. Copies of the documented program with sample output are available upon request from the author.
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'Daniels, F., et al, "Experimental Physical Chemistry," 7th Ed., MeGraw-Hill Book Co., New York, 1970, p. 68. ZIbid., p. 61-70. Swingad,R. E., et al., Ind. Eng. Chem., 47,1757 (1955). "thmer,D. F., and Jasefowitz,S.,Ind. Eng. Chem., 39,1175 (1947). Acetonitrile-water system data.
318 1 Journal of Chemical Education
MOLE F W C T I O H OF COMPONENI ONE
Figure gram.
1.
Acetonitrile-water iiquibvapor equilibria data as plotted
Figure 2. Optional tabular output
by prc-
