sponding instructions are available from the author. Send three International Response Coupons to cover postage to Dr. Eduardo L. Varetti, Area de Quimica InorgBnica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115,1900 La Plata, R. Argentina.
weight, can be obtained only when the polymer, a solvent, an osmometer, and a thermostat bath have been properly assembled. If osmometry and number-average molecular weights have been covered in class, the student will he reauired to vass a preliminary auiz. If not, the instructor may
Dynamic NMR Spectra of Two-Spin Systems
material to catch up in order to treat the data; both are pedagogically useful. The program requires good safety standards to he maintained in the laboratories. For instance, if safety glasses are not "worn" in any laboratory, the student is expelled from the building which is tantamount to losing all accumulated data. The program is written in APPLE PILOT and requires an Apple language card and an Author disk to modify the program. The program can he run on any 48K Apple 11. There are approximately 600 statements occupying 170 blocks which includes PILOT system information. Total solution of the problem generally takes several hours which has prompted us to include provisions for saving the current status in a file automatically created by the student. A description and program listing and copies of floppy disks are available. Send check or money order made out to the Department of Chemistry and Chemical Engineering in care of the author a t the ahove address ($5 for a listing; $15 for a listing and copy of the disk).
Richard A. Newmark 3M Central Research Laboratory St. Paul, MN 55144 The equations of Gutowsky and Holm (7) are used to calculate dynamic NMR spectra for two uncoupled spins undergoing exchange. The populations of the two sites need not be equal. The intrinsic linewidth (linewidth in the absence of exchange) correction is included in the equations. The program will list the spectral amplitudes versus frequency or produce a high resolution plot. The program will systematically iterate over tau, the lifetime of the spins in site A, to match the observed linewidth of the snectrum a t both slow exchange rates (2 peaks present) and fast exchange rates ( 1 peak observed). The program will also systematically determine the true frequencies (frequencies in the absence of exchange) - . of the two peaks a t slow exchange rates. The free energy of activation for exchange is calculated if the temperature is eiven. This program has been used a t 3M to calculate dynamic NMR spectra for simvle organometallic systems. It should he equallyc~pplicahleto organ; or physical chemical experiments in which dynamic NMR spectra are observed and serve as an introduction to the use of NMR in the study of dynamic equilihria. For example, the student can quickly reproduce the classic example of N,N-dimethylacetamide shown in most elementary textbooks and see visually how changing the peak frequencies, site population, exchange lifetime, or spectrometer linewidth affects the dynamic NMR spectrum. The program is written for a 48K Apple I1 Plus. The coding uses 300 lines of Applesoft BASIC and could he easily rewritten for other versions of BASIC since the graphics portion is only used to plot the NMR curve in a simple loop. Listings and nrogram conies on your disk are free: conies on mv disks ; are $3.50 e a c h . ~ e n dchecks to R. A. Newmark, 3 ~ Bldg. 201-BS-05, St. Paul, MN 55144.
POLYMERLAB: A Computer-Generated Problem Fred D. Williams Michigan Technological University Houghton, MI 49931 In order to review and to anticipate lecture material in polymer science as well as to simulate a series of lahoratory experiments, we have developed an interactive program using an "adventure" format. It is intended for seniors or graduate students. The student begins with an unknown polymer and must "search" a lahoratory building to acquire the necessary equipment and supplies to conduct experiments. The challenge is to identify the polymer and as many of its physical properties as possihle. Furthermore, prior to being permitted to conduct any experiment or test the student may have to mass a ~reliminarv "auiz . on the exnerimental material. The running program gives the student enough information to determine the emnirical formula. intrinsic viscositv. .. numher and weight average molecular weights, as well as a scanning electron micrograph and infrared and nuclear magnetic resonance spectra when appropriate conditions are met. As a typical example, raw osmotic pressure data, i.e., solvent height as a function of weight percent polymer that is used to determine the material's number average molecular
Programming Utilities for the APPLE II Plus Edgar H. Nagel Valparaiso University, Valparalso, IN 46383 Two machine-language utilities have been developed for the APPLE which greatly aid the use of the computer for Computer Aided Instruction (CAI). The utilities allow users to print upperllower case with suhscriptslsuperscripts and to type expressions a t an INPUT statement. The utilities require a 48K APPLE I1 Plus with DOS 3.3. The character generator was developed hecause CAI leaves something to be desired if it is all done in upper case letters. 1Tnnnr case can be added to the APPLE either bv ~- nnd - ~ - lower ~ making hardware modifications or by using the high resolution erauhics screen. Proerams develowed usine" modified APPLES are not as transportable as ones developed using software. Therefore, the character generator that was developed does not make use of any special additions to the APPLE. The eenerator and character set simwlv . . reside ahove page . . two of t i i t 1i:
