with access to larger computer systems may wish t o refine the model further. Completion of the refmement stage signals commencement of the OUTPUT phase of our program PAD. We use program PAD most frequently to create models of drug and substrate or inhihitor molecules. These models are then fit interactively into the receptor site of proteins and enzymes being investigated by this lahoratory (5).A second use involves the input of molecular structures t o program CHIRAL (6),which a ~ ~ l i the e s Cahn-Ineold-Preloe rules to determine chiral descriptors for stereogenic centers. The method involved in the develo~mentof vrwmm 1'AI) could have a direct auolication to the enormous data entry prohlems faced by chemical documentation moups, with the added benefit that full three-dimensional information may he input; most major chemical documentation efforts employ two-dimensional or vaguely three-dimensional representations, even though very few moleucles are truly flat, and lost information (i.e., dimensions) is difficult to restore at a later step without connidemhle ambiguity. Pnmnm PAD. written in Fortran N for the PDP11140 runs underk~~ll- with a Vector General 3DM display, contains 1149 statements and 151 comments. Execution requires 27100 16-hit words. Documentation includes source listing and thesis (7). Copies of the listing are available far $5; copies of the thesis are $15. Your 800 bpi magnetic tape can be written with FLX (PDP11 and VAX) for $10 uostane & handline. Make check to Biographies ~ahoratory;~ e ~ & t m e of n t~yochemistry and Biophysics, Texas A & M University, College Station, T X 77843. A simplified version of PAD has been written in PASCAL for the Apple I1 computer. A listing is available for $5 at the above address. This work has been generously supported by a grant from the Tektronix Cor~oration.the NIH. the Robert A. Welch Foundation, and tGe Texas kgriculturh Experiment Station. We thank Dr. Alton Banks for orovidine us access to the A ~ n l e I1 computer.
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Calculator Programs for Analyzing TGA Data J. E. House, Jr. lllinOls State University, Normal. IL 61761 Nonisothermal TGA studies have become i m ~ o r t a n for t determining kinetic parameters in all fields of'chemistry. However, analvsis of the data can he laborious and time consuming. The usual rate law is A da = -=-EIRTdT (1) (I-4" B where CY is the fraction reacted, T is the temperature ( K ) ,n is the reaction order, E is the activation energy, A is the frequency factor, and @ is the heating rate (8). Exact integration of the right side of eqn. (1) cannot be accomplished so there are several ao~roximaterate eouations that are used (9). One of themost widely used methods for treating TGA data ia that of Coats and Redfern ( 1 0 ) . In this method. the integrated equations are
when n = 1,and when n
z 1,
The value of a is calculated as an observed mass loss ( D ) divided by that expected for the complete reaction. The term In [(AR/E@)(l- (ZRTIE)] is very nearly constant. If we represent the left-hand side of eqns. (2) and (3) as ~ ( c Ythen ), a linear relationship exists between f ( a ) and 1IT for the correct value of n. T h e n E is found from the slope and A is calculated 518
Journal of Chemical Education
from the intercept. In carrying out the analysis, typical values of n that are of theoretical interest (usually n = 0,1/3,2/3,1, 413,513, and 2) are used and each f ( a ) is computed for each data point (tj,Dj). Linear regression of f ( a ) versus 1IT is then performed. Such computations are laborious and a programmable calculator speeds the analysis of TGA data enormouslv. T W types ~ of programs for programmable calculators have been developed. The first of these, CRPBP, is for use with machines having a limited numher of program steps and memories such as the Hewlett-Packard HP-25 and HP-33. This program involves entering a temperature and deflection (mass loss) data pair (t;,Di). The program then computes sequentially the value off (a) for n = 1,0,113,2/3,413,513, and 2. The next data pair is entered and f(a) computed for all the values of n. When the process is complete for all the data points, these f ( a ) values are used in linear regression or eraohical dottine aeainst 11T. - The second prigram, CRCOM, is for use with the Texas Instruments TI-59 and TI-58 calculators. I t uses 235 program steps and up to 60 memories, depending on the numher of data pairs. Up to 14 (t;.D;) data pairs can he used with the TI-59 and fou; data pairs can he ;sed with the TI-58. The desired f ( a ) values are computed and stored until all the data have been used. Then, linear regression is performed to determine slope, intercept, and correlation coefficient. The value of n is inciemented and the process repeated. The temperature and deflection data are entered only once and the seven values of n are used automatically. The value of n yielding the highest correlation coefficient is assumed to be the correct order. These programs will he useful to students and teachers in instrumental analysis, solid state chemistry, physical chemistrv. r and other amlied lahoratorv areas ...~ o l.v m echemistrv. using thermal analysis. using the pro&m, the analysis of the data takes no longer than obtaining the TGA curve and errors are reduced considerably when compared to computing f ( a ) values point-hy-point. Also, faculty memhers may find the programs useful for verifying students' results obtained by other methods and as a teachinc tool for instruction in data analysis for comparison of TGA ;esults with usual isothermal kinetic data. Finally, the programs allow practice in using hypothetical data in "dry lab" situations without spending a great deal of time in unproductive, repetitive calculator work. Complete listings of the programs and instructions for their use are available from the author a t the address given above. Send $2 (cash or check payable to J. E. House, Jr.) for the CRPBP promam (for HP-25 and HP-33C calculators) or $3 for the ~ R C O M for use with the TI-59 a n d ~ 1 - 5 8 calculators.
Library Orientation to the Technical Literature Patrlcla C. FlaL Paul Smith's College, Paul Smiths, NY 12970 A utility computer program has been developed to provide students in general chemistry with a basic library orientation lahoratory. Employers expect library know-how of our Ecology and Environmental Technology graduates. Several recent articles in THIS JOURNAL. (11-15). further attest to the need to orient students researching technical information in appropriate reference hooks, periodicals, files, or stacks. I use a library "experiment" as the first lab in the second semester of freshman general chemistry, a semester in which there is also a required "research" project which is an independent fact-gathering lab project hacked by a bibliography of material pertinent to the individual projects. Even with freshmen English in their curricula, students are not always able to exhaustively search the technical literature in the library. This "experiment" will help students learn to gather technical information in a systematic, organized manner. I
update the experiment each year by replacing questions older than eight years with ones from the current year. This also protects the magazines from overuse. After an introduction to the library and a discussion of the "experiment," students work individually on their "experiment" during the rest of the laboratory. A chemistry instructor answers questions and guides students, thus also assisting the library staff. The "exp&ment" has seven parts:
program with accompanying documentation and answers for all the questions is available for $3.00, or a cassette tape with corresponding answers and documentation is available for $10.00. An exchanee of chemistrv and environmental science programs is also disired by the author.
Part A: For the indicated question, students are asked to write a
complete bibliography. They are told that they will find all books in the card catalog.There are twenty-fivequestions; a student answers only one. For example, the following questions might be given: (1) To study the principles of polymer chemistry, one should select whnt hook? (21 If vuu ore interested in learning nhout some the chemistry of rhe Manhattan l'rojrct, to whnt hook will you turn" ~~~~
Computer Programs for Introductory Quantum Chemistry Bhatrav D. Josh1 State University College at Geneseo Geneseo. NY 14454
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Port B: Using the "Reader's Guide to Periodical Literature" or a
December index, the students are asked to write the complete literature reference for the following articles: (1) Grinstead, R. R., "Bottlenecks." (2) Flath, P. C. and R. Uhorehak, "VersusNersus-A Lab Students Don't -.~ . - -D~end.'' ~ ---There are 57 questions in this section; a student is assigned two. (Use Sciquest, Scientific American, Enuironment, or THIS ~
Part C and Part D: Both of these parts involve the four journals
previously indicated. A description of the article is given and students start with kevwords tosearch for the article. Part C has 44auestions from ~ciouebt.Scientific American or Enuironment. A &dent anmight be given: (1) A 1973article discusses the problems of removing CO from auto exhaust. Has success been achieved in this project? Cite the article. (2) Cite a 1977 article by an author from one of our sister two-year colleges in northern New York on planning a hazardous materials course for local firemen. Name the author's college affiliation. Port E: From a list of twenty-five terms, a student is asked to define
one term and give the complete reference. The answer will he found in one of many reference works available in the library. The following are terms that might be used: (1) Define Sulliuon's Test. (2) Define smoltite. Port F: Fnm a list of twrnry-re\.rn quesriona a ~tudentmust search t h o "Handhook of Chemirtry and Physics" for the answer tu hi* assigned quesuon. For example,he might he asked the Idlowing qurs-
tions: (1) Which is denser-water
or 4-methyl-2-pentanone? (2) How many BTU's in an erg?
Port G: Similarly, Part Grequirea a student to search the "Handbook" for the answers to one of four different tvnes of ouestiaus. For ex-
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ample, the following questions might he given: (1) The solubilityof 1-alanineis -grams1100 grams of water at 25%. (2) Constants for babassu oil are specific gravity -iodine value saponification number melting point T h e "exoeriment" has been accepted and enioved bv the majority oE students over the past tkn years. ~ o scomment t about finding new (to them) ways of searching the literature. The largest problem for me has been the mechanics of making sure each student receives a different set of questions. This year I put all of the questions into one computer program and then printed sixty lists of randomly selected questions. With my printer I have hard copy, but it could be done with a CRT if no printer were available and the question' numbers copied onto a pretyped form. The program is written in BASIC, specifically for a Model I, Level 11, 16K TRS-801 microcomputer. A listing of the
' TRS-80 is a trademark of the Tandy Corporation.
James E. Ellers State University College at Brockport Brockport, NY 14420 For the past two years we have been involved in the development of a set of comouter oroerams in auantum chemistrv. The purpose of this prbject & tocreate a facility that will free the student from time-consuminamathematics so that he can concentrate on concepts, pri&iples, and techniques of quantum chemistrv. T h e set of computer programs we have developed generates data, solves equkions, graphs solutions, and asks leading questions. I t also includes numerous lessons and drills on qu-&tum chemistry concepts and mathematical methods used in the study of quantum chemistry (16). The ouantum chemistrv- nroerams oackaae is beine de. signed for real time operation from interactive computer terminals by students with no required programming skills. T h e programs themselves are written either in interactive FORTRAN to run on PRIME 400, or in APL to run on ITEL AS16 under OSIVS1. The package contains service routines, limited task routines, teaching routines. drill-practice routines, and monitor and control [outines. 1n able 1we present an alphabetical listing of all programs developed and tested thus far. The following abbreviations are used in Table 1: RR for "rigid rotor," P I B for "particle in a box," and SHO for "simple harmonic oscillator." Listings of the programs will be made available to interested readers for a $5.00 fee to cover duplication and mailing charges. Please contact B. D. Joshi. This work is suooorted. in part. bv grants from the State Cniversity of ~ e w i ' o r k~ & r c h kida at ion: # 125-1006A, it 12WWtiH. It 1%-JW8A. and it 125-4WXH.Ihanks are due 1)r. I.w'l'.lksant ot'the (;en&(, (.ornputing Center tor his continu(rui and enthuiiaitic iupuort of this work. B. D. doshi is grateful to Barbara Joshi fo; h e r encouragement and unflagging support.
Extended Hiickel M.O. Calculations for Classroom Demonstration John P. Cheslck Haverford College, Haverford, PA 19041 Molecular orbital theory in various forms is the basis for discussions of bonding and structure in manv chemistrv courses. Simple ~ i i c k e l i h e oisr ~used for discussions of plan& pi-electron svstems, with modifications oermittine discussion bf the effects of hetero (noncarbon) atoms on thepi-electron molecular orbitals, energies, and pi-electron charge densities. McGrath. Kroeeer. " , and Dunn (17) have described a BASIC program package to explain the theory with a small computer Volume 59
Number 6
June 1982
517
