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i f AX1 goto blank if AX1 I . a? pot0 h.LP f i n d .XI. c:\CHEH\MHICLY.TXT shift i f AX1 A goto i i n i
)
Cx\cn3\cn3.TR
The program may be used independently by individual students either before or, if necessary, in place of actual lahoratory experience. Active response of the instrument on the screen adds to the interest and personal satisfaction of the user. Even with the full availability of actual instruments a simulation may he advantageous. Adequate monitors can allow the instructor to demonstrate orooer . use of an instrument to an entire class at one time. One major advantage of a comouter is flexihilitv in shou.ine rather than simnlv telline. can provide kfficiel;t used as a visual aii, a introduction to routine operation, giving the instructor more time to fill in details of other experimental considerations. A program may offer activities that are commonly supplied hy the user. Recording and plotting data may be simplified so the beginning student is better able to consider significance rather than mechanics. I t is also possible to provide immediate information and suggestions concerning technique and interpretation of work as it is performed. SPEC20provides a highly interactive simulation of the Bausch and Lomb Soectronic-20. Written in BASICA. i t runs on the IBM-PC with a standard color graphics adaptor. Theentire instrument (Fie. 9)isdisolaved . - in 640 X 200 hiehresolution graphics with appropriate prompts at the top and bottom of the screen. The instrument and cuvette manioulation are fully animated and the instrument responds &mediately to all commands. Considerable attention has heen paid to details of operation and response. The instrument provides a "light source" mimickine the soectrum of an incandescent lam; that must he t u r n e l o n and allowed a brief warm-up befhe the dark current can he adjusted. Opening the lid to the sample compartment allows "outside light" to be registered on the meter. Small random errors occur if cuvettes are not cleaned and aligned at each insertion. One can choose asample andinsert it any any time with no problem, but the instrument will of course not respond unless it has been turned on. I t does not complain about failure to zero the dark current before beginning measurements, but this will show up in the results. Setting the zero with the sample compartment either open or containing a cuvette is also a possihility, as is changing the wavelength without resettine 100%Taeainst the blank. several consid&ed compromises have been made. The wavelength display is digital, the meter face shows % T but
.
an
echo PET R+diochwistry M i n i - M n l i n e Databas. echo echo ..re < C:\CKM\CHEn.TPP d r l C:\CMH\CHEH?.TMP > NlL: :end
Figure 8. Listing of CHEMBAT.
nounds. Thus. the auerv >CHEMfluor chlor benzene would ietrieve hoth fluor&hl&obenzeneand chlorofluorobenzene, while >CHEM meth chlor would retrieve both methylene chloride and dichloromethane. Similarly, queries seeking information on all acetate salts (>CHEM ocer INOR) or all three-carbon-containingalcohols (>(?HEM C301) are readily input. Additions or deletions to chemical stocks are noted on a bulletin hoard for inclusion in the database file. An updated datahase file is produced from time to time as follows: records are revised or addedto the data file; (if a printed copy is desired. amacro to sort the records is executed): the data file is merged with the primary merge file containing formatting information; a macro-to-strip unnecessary control codes is executed; (optionally, the file is printed); finally, the file is saved in ASCII form for searching. The procedure described is sufficiently general and convenient that an on-line database for chemical inventory is now within reach ofany laboratory with access to a microcomputer operating under MS-DOSand can be implemented within a short time without costlv software or sonhisticated orogramming skills. ~~~~~~
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SPEC20: A Highly Interactive Simulation of a Manual Spectrophotometer Ralph W. Gable Davidson College Davldson. NC 28036
Simulations of sophisticated laboratory instruments such IR (10,12), and HPLC (11) present an instruas NMR (9), ment, allow the choice of sample and parameters, and then run accordingly to produce output, usually in graphical form. A realistic simulation of a manual spectrophotometer, on the other hand, should show immediate instrument resnonse to each choice. The need for interactive eranhics ];resents a pressing challenge. Programs by Kelter a n d ~ a r r (13) and by Breneman (14) have moved in this direction by providing experiments using somewhat limited simulations of a manual instrument. the Bausch and Lomh Snectronic 20. Although even realistic simulation cannot serve as a full substitute for hands-on experience, it can provide a reasonable degree of familiarity with operation as well as theory. 26
Journal of Chemlcal Education
Figure 9. Screen dump of spectrophdomster display with cuvene ready for wiping and aligning.
Transmittance us. Wavelength Cobalt(1I)nitrate 8.2BB molar
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Reveal the curve?
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llbsorbance us. Concentration Cobalt
