Chemical Educcltion: Software The Acid-Base Package: A Collection of Useful Programs for Proton-Transfer Systems Rlchard W. Ramette Carieton College Northfield, MN 55057 "The Acid-Base Package" consists of four programs that deal with the types of acid-base calculations normally encountered in introductory and analytical chemistry courses. It also includes three utilities that complement the calculation programs. FABTIC, the Final Acid-Base TItration Curve program, calculates theoretical titration curve data for any mixture of acids and/or bases, using strong acid or strong base as titrant. A disk me, ACIDBASE.LIB, contains 126 molecular substances with their pK values, molecular weights, and formulas, from which the user can choose. Initial volume and concentrations, titrant concentration, pH range to be included, precision of the data, and whether to include the effect of ionic strength on activity coefficientsmay be set by the user. Calculated data may be printed and/or saved in a library disk file. ALPHA plots species distribution curves for protontransfer systems and for metal-ligand systems. Each species in the system will have a curve showing the fraction of the total that it represents as a function of pH (or as a function of lieand concentration for metal-lieand svstems). Plots mav he made with either linear or loiarithmic representation. like FARTIC. ALPHA aetr - DK . data from ACIDBASE.I.IR. BUFFPREP offers guidance for the preparation of pH buffers. The user specifies the substance (ex., citric acid or ethylenediamine), the desired pH, ionic strength, and volume, and the program indicates quantity of the substance to be used alone with the calculated amount of strone acid or strong base required to achieve the desired pH. In second mode. BUFFPREP can search ACII)HASE.I.IR for all suhstances technically suitable for preparing a buffer of aspecified pH, and then the user can make a choice. PHCAL is perhaps the most useful for the myriad pH calculations taught to high school students and undergraduates. I t deals with the seven fundamental types of solutions: neutral solute, strong acid, strong base, weak acid, weak base, buffer, and ampholyte. The user specifies pKvalue(s), concentrations, and whether or not to include ionic strength effects, and the program produces the pH and other related quantities at equilibrium. CURVPLOT is a eeneral nurDose ~ l o t t i i eoroeram that conveniently plots tiikation c;rvks calcu~atedb;FABTIC. ~t ranalso plot anvother X-Ydatanomatter what the raneeof the X i d Y ;dues. Up to 10 data sets may be plottcd at once, and each may be represented as a smooth curve, as small points, or as large points. The user has complete control over axis scaling and labeling. Any data set may be plotted together with its first derivative and/or inverse derivative. A useful feature of CURVPLOT is the use of "cross hairs" to read the X, Y coordinates at any point on the plot. They may also be used to mark any region of the plot for
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expansion, which is valuable for precise endpoint evaluation. XYFILE is a utility that makes it easy to prepare data files for plotting by CURVPLOT. It provides options for adding, deleting, or changing data points in existing files and for printing a file. SEARCH is a program that can search ACIDBASE.LIB for substances that meet a combination of specifications provided by the user. For example, it will find all diprotic acids that are in a certain range of molecular weights and also have one of their pKvalues in a certain range. It will find all acids containing a certain element, or all acid-base indicators with the centers of their color change intervals in a certain pH range. It also makes it easy to make additions to the library file. "The Acid-Base Packaee" comes with full documentation of tbeseprograms, as well& discussion of fundamental principles of titration curve calculations, the importance of ionic strength, suggested laboratory experimenis, and examples of assigned exercises.
About This Issue John W. Moore University of Wisconsin-Madison Madison, WI 53706
"The Acid-Base Packwe" is a versatile. comorehensive set of programs that will be useful to students add teachers in any course that deals auantitativelv with acid-base eauilibria. A few examples wiil illustrate
