Computer Calculations in the Quantitative Analysis Course Laboratory Exerclses For the traditional beginning quantitative analysis course emphasizing gravimetric and titrimetric determinations, we have preExperiment Program pared and used a series of computer programs, written in BASICPLUS for the Digital Equipment Corporation PDP 11/40 computer. 1) precipitation of ~ i ~ k ~ l GRAVNI These calculate, from student data, the desired results of each as- 2) prep,ataion of standard HCI HCLSTD signed experiment In the ten-week course, nine different experiments ~ ~ t , I ~ sada ~ ~~h ~ i ~ ~ SODASH t i ~ ~ are carried out by each student. A series of programsallows each 3) ation ion of standard N ~ O H STNAOH student to enter hisher data and have the desired results calculated. VINEGR ~ ~ t ~ ~ m of i ~vinegar ~ t i o n Input for these programs is in the form: crucible weights, precipitate KA &eights, gravimstric factor, titrint volume, titrant normality, sample 4) ~,,l,bi~ GALSOL of C~SO, by cation Exchange weight or volume, etc. Output from these Programs is in the form: 5) precipitation of sulfate SULPRE percent desired component, concentration desired component, etc. 6) preparation of standard EDTA HDWATR The programs, in addition, tabulate mean values and relative average water ~ ~ r d ~ ~ ~ (parts per thousand) deviation. Two of the programs, a potentiometric 7) preparation I RAZOR , standard C~(VI) titration ofvinegar with standard sodium hydroxide and colorimetric ~ ~ t ~ of ~ tmn ~ ini a ~ a r~om r t d ei ~ n determination of iron, have plotting routines. These allow the Po- 8) preparation of standard Iodine ARSNIC tentiometric titration curve and/or derivative curve and the iron Determination of Arsenic absorption spectrum andlor Beer's law t o be shown graphically. In 9) photometric ~eterminatianof imn in a FD~OMR the ease of the titration curve plot, the student must read values from Vitamin the graph t o allow, through use of another program, calculation of the ionization constant for acetic acid. These programs have proven useful in our teaching of quantitative analysis. The programsthemselves, as presently written will query the student if, upon entering hisher data, a particular value is unrealistic based upon the known (to the instructor) outcome of the calculation. This corrects for possible gross errors a student might make in trahscrihing data a t the computertwminal.' The programs allow some flexibility by the student to alter the laboratory directions, for example, the number of repetitive samples can be varied. They donot, however, offer suggestions for assisting with intermediate steps in the calculations. The programs also give students practice in working with computers. From the instructor's viewpoint, the printouts for each experiment provide a consistent format thus facilitating grading. At present we have not undertaken computer gradingof the student data, however, programs for doing so have been developed successfullyby A counting subroutine included with each program allows us to know the number of tifnes each program has been called. For instance, the Sixty-four students enrolled the first time these programs were used called the first program a total of 394 times! This number decreased as students became familiar with the course and with using the terminals. The nine exercises assigned in our laboratory are listed in the table. A total of twelve programs are used to perform the calculations associated with these exercises. These programs have proven mast useful to us in instructing beginning students in quantitative analysis. Copies of laboratory directions and computer listings and printouts k e available to interested readers from one of us (GAP). The authors wish to thank the students and laboratory instructors who first implemented these programs through their development stages and Dr. Frank Walmsley and Dr. H. Bradford Thompson for their assistance and suggestions. This feature of the programs was suggested by the reviewer and enhances the implementation of these programs by ~tllrlentq -.. .........
Dcutioh, J. I... and Zalernnk, H. N., "Computpr Assisted I.aborntory Grading," Third Rirnninl Confprence on Chem~cal Educatim. Pennrvlvania Sclte I.'nwersity. University Park. PA., July 1974. Hughes, H. G., and Rundsrhuh,.J. E...I. ('HEM ED[.'(:.. 35.:1:16 119;8j. Jones, D. E.,and Lytle, F. K.,J. CHEM. EDUC., 50,205 (19-3). University of Toledo Toledo, Ohio 43606
David R. Martinez Abraha Bahta A r t h u r H. Black Gordon A. P a r k e r
Volume 56. Number 5, May 1979 1 309
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