MICROCOMPUTER GRAPHICS IN CHEMICAL EDUCATION

Note: This article was scanned using OCR from the Fall 1986 CCCE Newsletter. Please contact us if you identify any OCR errors.

          Microcomputer graphics are being used currently in several ways in chemical education software. Of course, microcomputer graphics can mean something as trivial as the display of the letter A on the axis of a graph or as complex as the display of a smoothly rotating molecular model.   In this survey, the examples are taken from readily available software for the Apple II or IBM-PC series of microcomputers.

          The simplest way that graphics are incorporated into software is as a static image used to illustrate some point.  The image is prepared using a drawing utility such as Koala Painter and then stored for later use. This is by far the most common use of computer graphics and, although simple to produce, many more programs could benefit from this kind of graphic usage. It is easy to recognize because the images are commonly stored on disk so that the drive goes on and there is a short delay just before the image appears. Typically, such a program could show a Periodic Table on demand or a title page with an attractive image on it.

          The better examples of the use of static images show up in the instrument simulations. These are intended for a tutorial or practice in the operation of a particular instrument. They can be useful when a student must practice the operation of a particular instrument before actually being allowed to operate it or when an instrument is not available but the skill to use it must be acquired anyway. These simulations can be relatively simple like theIR simulator of Krause for the Macintosh (SERAPHIM MC1301). The user can control sample concentration and cell thickness before the simulation plots the spectrum of one of the available unknowns.  A section of the program permits the user to make his own solution cell. The available parts have to be assembled in the right order and with some degree of precision.

          More complex are the simulations of Paul Schatz (University of Wisconsin). The IR simulation mimics the Perkin-Elmer Model 1310 and the NMR models the Varian EH-360 instrument.  The user must examine a mock-up of the main instrument panel and adjust the appropriate parameters just as in the actual machine.  Then the spectrum is plotted.

          HPLC by Rittenhouse and SPEC20 by Gable are under development through SERAPHIM. The former makes extensive use of very detailed, largely static images to simulate a High Pressure Liquid Chromatograph. The latter simulates the Spectronic - 20 visible-U.V. spectrophotometer. XENON by Whisnant (SERAPHIM AP606) simulates a vacuum line in which xenon and fluorine can react to form either or both of the xenon fluorides depending upon the temperature and concentration of the reactants initially chosen by the student user.

          The most complex simulations use interactive animated graphics when the image on the screen responds to user input either directly, or indirectly, in that the image depends upon variables entered. The earliest examples were the Chern. Lab. simulations of Gelder. The one which illustrates the gas laws allows the student to vary P, V, N and T and to watch the simulated gas respond.      Other modules available include acid-base titration, calorimetry and experiments involving equilibrium reactions. The simulations of Rittenhouse tend to favor re-enactments of famous historial experiments such as those of Rutherford. The user of this software can design and implement experiments on alpha particle scattering. The Rittenhouse simulations are excellent in that the graphics are very good and the user has to do the kind of thinking that the original experimenters did in order to reproduce the original results. The opportunity exists to accumulate extensive data from which the significant results must be culled.

          The animated simulations of Bendall are not so difficult for the user. The objective is made obvious and the program is much more linear, reducing the possibility of being side-tracked.  A typical example is Backtiter (SERAPHIM AP604) in which the object is to determine the con entration of carbonates in a mixture by adding it to standard acid and back-titrating the excess. The simulation requires the user to weigh samples on a top-loading balance and to titrate using a simulated buret.  Along the way, the carbonate is shown bubbling as the acid is added, the buret flame flickers and the gas is shown escaping when the carbonate is heated.

          Molecular modellers illustrate another use of microcomputer graphics. Typical of these are MOLEC by Owen and Curry and Molecular Graphics by Henkel and Clark. MOLEC was reviewed in J. Chern. Ed. in September 1984.  Molecular Graphics can display and manipu­ late structures with more than a thousand atoms and bonds. The image can be translated along any coordinate, rotated about any axis or bond, enlarged or reduced. Standard molecules such as chymotrypsin are available, or one may enter a molecule by supplying atomic coordinates and bond connection tables. The image can be space filling in which case each atom is represented by a large sphere or made up of lines or lines with a small sphere at each intersection.  The structural manipulations are slow.  This is a common limitation of these packages.  The calculation and drawing of a new view depends upon the number of atoms but can take up to eight seconds and is too slow for effective animation. Space filling representations take longer to draw than line drawings.