Computer Simulated Titration Curves This note describes three computer programs for generating theoretical titration curves. These programs have been used in our analytical chemistry courses to supplement the discussion of equilibrium theory. The method of calculation is t o select a value far the dependent concentration variable, for example, the pH, and calculate the fraction titrated. The equation for a titration curve is linear in fraction titrated (or its equivalent, volume of titrant).' Thus, even titrations involving many simultaneous equilibria can be generated without resorting to restrictive assumptions or solving higher order equations. All of the programs were written in Fortran IV, double precision and were run on an IBM 360144. The output consists of a table of the negative log of the dependent concentration (e.g., pH) and fraction titrated. The same data is presented as a plot on the line printer. Although approximate, this plat is frequently adequate to illustrate the irnportant features of the titratian. The programs are: (1) ACID (2.9 K bytes) calculates the titration curve of a weak monofunctional acid with a stmng monofunctional hase. The concentrations of the acid and the base and the pK. of the acid are the variables. (2) POLY (3.4 K bytes) calculates the titratian curve of a polyfunctianal weak acid with a monofunctional strong base. The concentrations of the aeid and hase and the pK,'s of the aeid are the variables. (3) EDTA (0.4 K bytes) calculates the titration curve of a metal ion with ethvlenediarnine tetraacetic acid (EDTA). The metal and EDTA concentrations. the metal-EDTA formation constant i n d the oH are the inuut The oH is assumed to be constant . narameters. . throughout the titration. Listings of these programs are available from the author on request. 'Fleck, G., Proc. Canf. on Computers in the Undergraduate Curricula (June 1970, Univ. of Iowa). Johnson, K. J., personal communication.
C. E. Wilson Indiana-Purdue University Indianapolis, 46205
344 / Journal of Chemical Education
