the computer bulletin board Douglas Jones; a t Georgia Tech, Mary Trauner; a t NCSA (Illinois),Tony Baylis; Mike Krogh; Nora Sabelli. Portions of the soilware used were developed a t the National Center for SupercomputingApplications at the University of Illinois a t Urban-Champaign. The author gratefully acknowledges a grant of computer time under educational project # TRA900207N.
Updating an Old NMR Spectrometer Using an ISM PC Computer through the RS-2324 Communication Standard G. Movna and L. Mussio -~~~~-~ ~
~ainte6anceLaboratory Facultad de Quimica Avda. General Flores 2124 Montevideo, Uruguay Users of old FT N M R spectrometers (i.e., Varian XL-100, Bruker HX-90, ek.) have a very limited range of experiments to perform with their machines. Only simple Alternate Pulse sequences are possible. Data manipulation is very difficult and sometimes impossible. This situation is not rare for investigators in developing countries, where the possibility of getting new equipment is low and sometimes machines were purchased during less stringent financial condition. Hardware and Software Modifications Generally computers from the late 60's were connected to their TeleTypes via Current Loops working with relays a t 110 Bauds. The M M 620L TeleType Controller used in the Varian XL-100 FT spectrometer is such a case (10-12). The MC1488 and MC1489, two popular level converter ICs, were used in the modification, replacing the send and receive relays. The baud rate was modified by changing two pairs of capacitors from the send and receive clock signal generators in the TTY Controller board. To get the spectral data a t the PC an RS-232-C handler was necessary. A TTY emulator program has been customized in Turbo Pascal to satisfy our needs. Data is processed in a Turbo Pascal subroutine that is able to edit the spectra and calculagives us the possibility of making on-screen JHH tions and integrations, differencespectroscopy, and to save spectroscopic data by creating a spectra data bank. In order to make it possible for the M M 620L to dump the spectra through the modified TTY Controller, a little M M 620L machine language program that dumps the FID or NMR data table when called from the PC was made. All the original VDM 620L TTY program tapes were backed ' up in MS-DOS format. Conclusion Simple electronic modifications of the W M 620L TTY Controller and connection to a PC, transformed an outdated computer into a relative good data acquisition system. Spectral data now can be handled easily, because it can be taken in disks to the chemists laboratory, making printing and customizing fit to the users need. All the changes discussed here for the Varian W M 620L computer can be adapted simply to make similar improvements on other old NMR computer systems. The most important point to consider is that an old machine A78
Journal of Chemical Education
can be improved with a small amount of money The pmject had an overall cost of $1500 US, including the PC. This is important in developing countries such as Uruguay, where we have lots of time. but not so much monev. A lise ing of the original Turbo pascal program as well & prices and circuit dagrams can be obtained for the authors. Acknowledgment The authors wish to thank Jean F. M. 0 t h and Ignacio Stolkin (ETH, Zurich) for the organization of the donation of the original apparatuses. The encouragement and direct help of Gerardo Burton and Gustavo Arabethy (UBA, Buenos Aires), who also gave very important suggestions, is acknowledged. The support of the CEC through grant C11.0317.U also is acknowledged.
Using Communication Software to Capture Experimental Data Estel D. spraguel Thomas H. Ridgway University of Cincinnati Cincinnati. OH 45221
Many of the instmments used in our upper-level undergraduate lab courses are controlled by internal microprocessors, with no provision for storage of data on removable media. While these instruments provide ease of operation and convenient analysis of data for most standard procedures, it sometimes is desirable to treat the experimental data in ways not allowed for by the manufacturer. For example, the students in one of our senior lab courses carried out a kinetics experiment [recently described in this Journal (1311,which involves the flash photolysis of an organic dye. The thermal isomerization reaction occurring after the flash is followed bv monitorine the absorbance at a fixed wavelength as a Lnction of time. The expected functional dependence of the absorbance on time is A, =Aid + ( A , -A,, ) exp(-kt)
(1) where t is the time, A,, A. and A,F are the absorbance values a t times t, 0, and infinity, respectively, and k is the firsborder rate constant for the reaction. Because this exDression is nonlinear in one of the Darameters. k. a statistically appropriate analysis of the i a t a calls fir the use of model evaluation methods described earlier in this Journal (141, which make use of a nonlinear, least-squares program to fit the data to the appropriate expression. Since such procedures are unavailable in the spectrophotometer's software (Perkin-Elmer Lambda 4B), it is necessary to transfer the raw data to some other mi&owmputer 6 that the desired analysis can be carried out there. The most direct and obvious solution is to use the builtin functions of the spectrophotometer to print out the raw data, followed by manual entry into the other computer. This method clearly leaves much to be desired, both in the amount of labor required and in terms of the probability of introducing errors during the transcription process. Recently, we have been making use of a simpler method for instruments employing an RS-232 serial port for communication with an external ~rinter.The cable normallv con-
' Author to whom correspondence should be addressed Datastorm Technologies, Inc.
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