Updated Student-Use Programs for the Calculation of Mass Spectral Isotope Patterns 6. M. Mattson Creighton University Omaha. NE 68104
Edward Carberry Southwest State university Marshall, MN 56258 In 1973 we published a note describing a Fortran computer program that quantitatively calculated the theoretical values for the relative intensities of the mass spectrum peaks for compounds containing any of the first 92 elements (15). The most valuable feature of the nroeram was that isotope abundance data for all 92 elemen& wek a part of the program; the user only had to input the formula of the compound or fragment. We have undated and imoroved the oromam and it is now available in eortran and ~ a s i languag&. c The latter program uses interactive Aoolesoft 11. is 133 lines lone and accesses a TFILE that con&s the isotope abundance data. Documentation including listing, sample run, and instructions provided free upon request. Copy of program on APPLE I1 floppy disk (DOS 3.3) is $8.W (we will provide disk). Send correspondence to B. M. Mattson; checks payable to Chemistry Department. ~~~
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Plotting Titration Curves Using an Apple II Plus Microcomputer Roger Joseph Meyw and Rene Barone L. A. au CNRS 126 Universite des Sciences et Techniques de St. Jerome Marseille Cedex 13, France In the introductory chemistry course for first year college sciences at the University of Aix-Marseille 111 we have found that computer simulations serve as an excellent supplemental tool for learning chemistry. The program described here serves for checking the experimental results during the laboratory period. Numerous computer programs exist for the study of acidbase equilibria (9,16,17). The difficulty of choice consists of using either simplifying assumptions or algebraic complexity of accurately solving a cubic or higher order equation in (H+) (16. . ~ 18.19). , - ~ . These difficulties are easily avoided by treating the hydroeen-ion concentration as the inde~endentvariable (20-22). the method has been extended to ~ e c e n tinl ~THIS JOURNAL polyprotic acids and bases (23). We have utilized these relations to realize a program TITRATION CURVES for use on an Apple I1 Plus (48 K) microcomputer. We determine the concentration of the base added as a
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Figure 6. Molecular-ion isotoplc peaks represented as a histogram on a pocket calculator.
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Journal of Chemical Education
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function - - - of ~ OH. Values of nH are inserted at chosen intervals of 0.25 unit. Each curve is calculated continuously using only one equation. The computer plots the theoretical titration curves and calculates the concentration of any species present in solution for the values of K. and the concentrations indicated by the student. TITRATION CURVES has a main menu that includes the choices: 1) weak acid versus strong base, 2) diprotic acid versus strong base, 3) mixture of two weak acids, 4) weak base versus acid, and 5) triprotic acid. For each option the user can use the set of conditions given bv a secondaw menu. The propram is highly interactive and eiiminates thk need for the operator to have any special knowledge of computers. All the prompts to the users are in printer X is used. Frenrh. An E ~ S ~ ~82 M A hard copv is available and the printouts mas be trimmed and pasted the notebook as a permanent record. TITRATION CURVES is written in Applesoft Basic and has been successfully used by our students. It consists of 460 lines and uses about 13.5 K bytes of memory. Available from SERAPHIM. ~
Graphical Display of Chemical Interactive Programs Using a Programmable Pocket Calculator Davld HOtdSworth University of Papua New Guinea Papua New Guinea Recent innovations in pocket programmable calculators alnha-numeric characters enabline svmbols and words include -~ portable printer to be s t o r e d i d displayed (24). A allows a copy of program steps and tabulation of chemical data for permanent reference. Some printers, e.g., those for the Hewlett-Packard HP41C. enable graphical display using a preprogrammed plotting routine in the printer allowing interactive single plots of mathematical expressions of the form Y = f(X),some of which can he useful to chemistry students. Two examples of programs of this type used by chemistry students at the University of Papua New Guinea include ~~
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1) Titration curves. Simulation titrations of a strong or weak acid with a strong or weak base (25). 2) Mass spectra. Isotopic heights of molecular and fragment clusters of organic halogen compounds (26).
However, an inquisitive chemist investigating the uses of the printer can devise alternative programs in the calculator that use the printer solely to print the graphic o,utput in the format desired. Some examples used in chemistry tutorials at U.P.N.G. are described briefly. Histograms . These are often used by statisticians to compare data. A program can be written to print a column of a specified symbo1,such as a *,as a histogram on the print paper. There are 24 character spaces in the column of the printer described so the maximum data column reauired is dis~lavedwith 24. or fewer, symbols and other data vhues are muitil;lied by a factor to be appropriately scaled. The integer function is operated since the printer requires an integral number of symbols, W 4 . In this wav it is oossible to print htstomams r e ~ r e s e n t i nbar ~ graphs of mass spectra molecular ion isotopic peaks. Double Graph Plotting Many mathematical as well as chemical graphs require two or more functions to be plotted and intersections noted. I t is impossible to plot a quadratic and a straight line using the preprogramed facility in the calculator printer. However each line of the required plot, as X increases, can be regarded as two superimposed histograms where only the highest character space of each is plotted with different standard symhols such as * and # and the other "symbols" of each are blank spaces. If both prints are to occupy the same space, of 24, another symbol such as can be printed. This represents an inter-
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