ditd by:
WALTER A. WOLF Cdgate University Hamilton, New York
Simulated Student Samples GordonA. P a r k e r University of Toledo Toledo, Ohio 43606 Current emphasis on the world in which we live and our obligation to conserve its resources to the best of our ahility have awakened a new interest in the study of materials we find about us.'The student is, or should he, interested in, for example, the type and quantity of pollutants issuing from a manufacturing plant which effects the air we hreathe or knowledge of the function of various trace metals in our bodies, information necessary for helping to diagnose and treat certain diseases. Various natural substances can be used as samples for student investigation in his or her study of these and other concerns. Frequently these studies involve qualitative and quantitative analvsis of complex materials.-studies of this-type have, at some institutions. already. replaced those using. more traditional . samples to students. Samples of natural origin offer a considerable challenge to both student and instructor if accurate, meaningful analyses are to be performed. Unless one has a thorough understandine" of a particular s a m.~ l e. .including possible interfering effects of matrix components, the results obtained from determination of constituents present can he erroneous. Simulated samples are intended to aid in a student's study of a real sample. The mixtures are based upon actual standard samples taken from the literature where they were used in the study of a particular material. A student interested in studying a constituent in a certain available sample can perform his or her investigation first on the synthetic mixture. Experience is thus gained in the experimental techniques employed and better evaluation is made of matrix effects upon the results obtained. W ~ t hthis information a more meanineful intemretation of results should be possible from th;real sample for which no true answer is previousls known. Besides serving as standards for studying real samples, the simulated mixtures can themselves be used as samples especially in those situations where it would be difficult to obtain real samples. Directions for preparation of samples simulating animal tissue ash, coal ash, copper refinery flue dust, plant ash, rodent teeth ash, and soil ash are available from the author.
106
/
Journal of Chemical Education
A Computer Program for the Analysis of Titration Data D. M. Seholler Lebanon Valley College Annville, PA 17003 M. L. Lyndrup Lebanon Valley College Annville, PA 17003 A computer pmgram, TITRATE, has been written for student usage in our introductory chemistry and hiochemistry courses to analyze titration data for monoprotic and dipmtic acids. The program, written in interactive BASIC, employs an algorithm which is a modification of the second derivative method of the location of an equivalence point in a titration curve for the determination of the volume of titrant added a t the equivalence point using student titration data (oH versus volume titrant added). The ~ e n d e r s o n - ~ a s s e l b a l cequation h is then used to determine the equilibrium constant(s) . . for the acid from the volume a t the equivalence point and the experimental data. The volume of titrant added a t the equivalence point has been determined to within f 0.5% and the pK,(s) to within 0.05 unit for typical student data with an uncertainty of f 0.1 in the experimentally determined pH values. The program has been used for the analysis of monoprotic acids, dipmtic amino acids, and with minor modification for redox titrations. Copies of the program, representative student data, and results are available upon request by writing to M.L.L. a t the Department of Chemistry, Montclair State College, Upper Montclair, NJ 07043.
*
Kinetics Simulation Program G. L. Breneman Eastern Washington State College Cheney, 99004 The kinetics simulation program described by W. C. has been rewritten in the Basic language. The program simulates the spectrophotometric study of the rate of the reaction Cr(HzO)5Br2+ + U3+ CrZ+ + U4+ + Br-. The rate law is of the form Rate = k [ C r ( H ~ o ) ~ BrZ+]O[U3+Ib[H+Jc. The student choose3 concentrations and volumes of the reagents, wavelength, and cell path length. The computer outputs observed ahsorbances for times specified by the student. From this absorhance data the student must determine the values of k, a, b, and c in the rate law. The program helps the student analyze the data after each run by offering an initial rates calculation and/or least-squares fit of any or all of 8 functions of absorbance versus time to the data. (This differs from Child's original version which displayed a plot of the 8 functions.)
I Child'
-
This program was used by 10 physical chemistry students with great success. They were able to complete the experiment in much less time than would he needed in the lahoratory hut at the same time they had to make all the experimental decisions and use the same logic involved in the real thing. A complete listing and a student handout are available from the author. The author would like to acknowledge the detailed flow chart furnished by W. C . Child, Jr. that made this work possible. Child, W. C., J . CHEM. EDUC.,50,290 (1973).
A Creative, Research Approach to the Undergraduate Biochemistry Laboratory Paul Melius Auburn Uniuersity Auburn, Alabama 36830 In an effort to stimulate student interest and to provide a new approach intended to indicate the total process the scientist is involved in, we have introduced some unique procedures in our laboratory work in undergraduate hiochemistry laboratories. In place of the usual procedures, we now require two reports per quarter written in the style of a current research Journal preferably in the stu-
dent's own area of study: such as the Journal of Pharmaceutical Sciences and Journal of Pharmacy and Pharmacology, for the pharmacy student; Journal of Microbiology and Journal of Physiology, for the biologist; Journal of the American Chemical Society and Journal of Biological Chemistry, for the chemist or biochemist. The student is required to conform to the editorial suggestions of one specific journal. We have found the quality of the written reports to he vastly improved under these circumstances and reviewing and grading these reports is a much more interesting process. Some compromise or modification is required in many instances on preparation of figures. There is a tendency for the students to present data in a piecemeal disorganized fashion. They will have to he advised to combine data in the most informative and efficient way. The laboratory work is so designed that a project can be broken down into 2 4 three hour units. For example on glucose analysis by the 3,5-dinitrosalicylate reaction the first period is spent obtaining data for a standard curve which is analyzed by the least squares method. At the same time the student analyzes an unknown solution of glucose prepared by the instructor. The second lahoratory period is spent on determinine effects of temoerature. reagent concentration, glucoseconcentration and timk of reaction on the dinitrosalic~latereaction. The third lahoratory is concentrated on the analysis of urine and blood samples, preferably the students' own samples.
Volume 52. Number 2, February 7975 / 107
