and have requested more extensive replacement of conventional tests. Although some glitches in the data bank surface occasionally (such as print or answer errors) the didactic benefit of enhancing general chemistry instruction with this transferable svstem amears certain. As Shown &the functional flow diagram (Fig. 1) the 5l/4inch MSDOS svstem consists of a COMPOSE disk for exam generation, a TEST disk (written by COMPOSE) for student use and the SOCRATES question bank spread over six individual disks. The SOCRATES index (called TALLY) for the 8500 items in the bank resides on COMPOSE. Before generating an exam the instructor should select from this index the appropriate question file number for each topic. Consequently, a hard copy of the TALLY file is certainly advantageous for efficient exam generation. Machiue-readable copies of the examination system may be obtained by writing to the corresponding author. Acknowledgment The authors would like to thank R. E. Seevers and Ed Williams for valuable technical advice and programming assistance throughout the development of this project. This paper was presented in part a t the 41st Northwest Regional ACS Meeting, June 16,1986.
Computerized Checking of Data in Undergraduate Laboratories D. A.
Alkens, R. A. Balley, and R. L. Strong Rensselaer Polytechnic Institute Troy. NY 12180
An aoolication of oersonal com~utersthat we have found to he v&ahle in the ;ndergraduaie laboratory is checkingof data for acceotabilitv. As we have emoloved this conce~t. the student enters the raw, measured data and receives & immediate evaluation in terms of acceptable/unacceptable-repeat. If unacceptable, there is generally enough time remaining in the laboratory period to repeat measurements as necessary while the apparatus is still set up and solutions are available. Such checking provides an impetus for improved technique and ensures that the results will be able to illustrate those principles that the experiment is intended to address. We frequently follow this checking program, which gives only yeslno answers, with other computer manipulations of the acceptable data. An example of a physical chemistry experiment to which we have applied this approach is that involving electrolytic conductivity. In this standard physical chemistry experiment (3-5). the cell constant of a conductance cell is determined by measuring the conductance of a standard KC1 solution, and the conductance of strong and weak electrolvte solutions (HCI and acetic acid) are measured over a range of concentrations. Such measurements can be made quite accuratelv. but thev can also be verv ~ o o ifr techniaues are carelesi. In our program, students "cieck their cell constant determinations by entering the cell number, KC1 concentration, and conductivity meter readings for KC1 and for the distilled water used in the solution preparation. The known cell constants for all of the cells are stored in the program, which calculates the student cell constant and compares i t with the appropriate value. Agreement within 1%is taken as acceptable. his approach has clearly resulted in an improvement in the quality of data appearing in the student's reports. In the semester preceding the use of this program, approximately 30%of the final reports received exhibited major deficiencies in the form of excessive scatter in the data or values differine from the literature value by 5% or more. Another 10%initial-
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ly reported data that clearly resulted from experimental blunders, such as mislabelling of solutions. The program eliminates all such problems. Repeated measurements have not been unreasonably burdensome, and students clearly spend more effort to get it right the first time. We are using similar programs for a vapor liquid phase diagram experiment (6-8) (checking refractive index values making up the calibration curve used for analysis), and two kinetics experiments (hydrolysis of t-butylchloride (9, 10) and neutralization of nitroethane (11,12)). The decision as to what constitutes acceptable quality results in a teaching laboratory is sub.iective. Except for the conductance experiment, where the standard is based closely on a realistic evaluation of likely sources of error and the students are second-semester iuniors with considerable laboratory experience, we have set our limits to reject the worst 5 to 1070of the results. Such a limit eliminates blunders and gross carelessness, without resulting in excessive requirements for repetition. Results from students with different levels of expkrience or with different equipment might require more or less restrictive limits. In addition, we do not insijt [hat all acceptable results be excellent: there may still be a range umhen the results are ultimately evaluat. of grades . ed for quality. A demonstration disk (IBM-PC) of these programs can be orovided if reouests are accomoanied bv a check for 55.00 to cover handlini costs, made payable to ~ e p a r t m e nof t Chemistry, Rensselaer Polytechnic Institute. Acknowledgment We wish to thank Rensselaer Polvtechnic Institute for providing support for the development of these programs under the Harlan and Lois Anderson Courseware Develonment Grant.
A Student-Generated Database for the Physical Chemistry Laboratory J. A. Wood The Polytechnic Queensgate,Huddersfield.HDl 3DH, United Kingdom
. .. Bv the time students enter ehemistrv courses.. man",~~ are quite adept at pmgramming. Students shmlld hnve o p p o r r u n i t w to use the,? skills within the chemistry rlsssnmn. One w q m dc, this is to give students pnjects that arp related t u the wntenr currently being studied. In this way, chemistry students can use their computer skills to produce software for future classes (13). This is a policy actively pursued with our undergraduate students. By the time they come to the physical chemistry laboratory sessions they have almost finished their basic programming course and it is an ideal time for them to put their newly gained expertise to use. A variety of programming and interfacing exercises have been set as part of this course, and a number of these have been developed into standard laboratory progams in later years after suitable, often minor. amendment. The one described here has proved very popular with students and combines an application of programming skills with an exercise in reference literature searching and data retrieval, the product being a useful database of phvsical . propertv - .data. At each laboratoiysession a pair of students is given the task of compiling a table of data from literature sources available in the departmental chemistry library. They convert this to aBASIC program and then transfer i t to a disk to form part of a growing collection of such tables compiled by other pairs of students, all the data being relevant to lahoratory exercises currently in use, for example, melting points of common solids, boiling points of organic solvents, densities Volume 65 Number 4
April 1986
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of oreanic solvents. dissociation constants of acids, indicator pH ;nges, transport number of H+, molar ionic conductivities. standard half cell potentials, solubilities, and activity coefficients. The database is menu driven, each new additional table heing added to the contents display and becoming accessible to all future users of the database. The students are marked on accuracy of the tabulated data, whle layout, inclusion of correct units, mention of any relevant conditions, and reference to the source of the data. Thus not only does the exercise provide an opportunity to apply programming skills but it also serves as an introduction to computerized databases; i t combines library work with experience in selecting appropriate data and accurately reporting all relevant conditions applying to the data, and also it acts as a prompt to encourage making reference to literature values in their laboratory reports. The author will be pleased to supply further details on request.
A Microcomputer-Based Temperature Probe Chla-yu Lil and Oun-meng Zhuang East Carolina University Greenville, NC 27834 A circuit interfacing a temperature probe with an APPLE IIe comauter has been develoaed. The maior com~onents used in {he circuit consist of adheatstone bridge, twb operational amalifiers. an eiebt-bit intenratinn analoeue-to-dipitalconveier, anda pro&ammable 6520~&iphe&Ilnterf&e Adapter. A silicon transistor whose metal casing is used as the temperature sensing probe forms one arm of the Wheatstone bridge. The impedance between the collector and emitter of the transistor varies as temperature changes, thus creating an imbalance of the bridge. The hridge output is amplified by the op amps and digitized by the ADC before it is sent to the computer's peripheral I/O slot. The temperature response between 0 and 100 OC is extremely linear (correlation coefficient = 0.99994) with a resolution of 0.39 "Clstea. Better resolution can be achieved if calibrated with a narrdwer temperature range. The device has been successfullv used for the determination of the specific beats of metals. The same circuit can also be used as a digital data acquisition device for low-frequency analogue signals (maximum sampling rate 2 mshyte). Short machine language programs, whichare callable by BASIC,are required to drive the interface circuit. Full details are available from Project SERAPHIM.
Microcomputer-Controlled Automated Sampler Shahrokh Ghaftari Mount Mary College Yankton, SD 57078 As a Dart of a microcom~uter-AFinterfacinn proiect, an automa'ted sampler for t h e nebulizer of an atomic fluorescence s~ectrometerwas desinned. This sampler is designed fur a two-solution system (hiank/sarnple) and is ideal when alternate blank/sample measurements are desired. The introduction of each solution into the flame is controlled by the software. The system is simple and easy to build and has applirations in other interfacing projects such as an auto-buret for titration or for introductionof reactants into a cell for a reaction study. The three parts, A, B, and C (Fig. 2) are installed inside a 5" X 8" X 4" aluminum box; no other parts except tubing are required. Auihor to whom correspondence should be addressed. 344
Journal of Chemical Education
Flgure 2. Schematic of components for automated sampler. A. SPST microcube solidstaterelay switch: Grayhill, Inc.. 561-T Hill Grove Ave.. Box 10373, La Grange, IL 60525. 8. Three-way solenoid valve: Serlal number H02-726 Skinner Precision Ind.. Inc.. 95 Edgewwd Ave., New Britain, CT 06050. C. Three-way slide valve: Dianex Co., P. 0.Box 3603, Sunnyvale,CA 94088.
Figure 2 shows a single-pole single-throw relay switch is used to turn on and off the ac power to the three-way solenoid valve. The solid-state relay is controlled by one 1iO line, which goes through a TRI-STATE buffer (not shown) before going to the contiol input of the relay. A logic 1signal on the I10 line switches on the relay and hence the solenoid valve that directs air (-40 PSI) to a three-way slide valve. The slide valve moves, and this causes the output of the slide valve to be connected to innut 1 (blank). The output of the valve is connected to the b k e r nebul'er with 0:5 mm i d . tubinn. When a loaic 0 sianal is connected to the control input; the output of the solenoid valve is connected to the atmosphere and the output of the slide valve is connected to position 2 (sample) through action of a spring.
A Simple Electronic Interface for Wlreless Chemical Data Communications Lee Hln-Fat, Hln-Cheung Lee, Kuen-Cheong Au-Yeung, and Hon-Tsang Chan Hong Kong Baptist College 224 Waterloo Road. Kowloon, Hong Kong Many undergraduate students may be interested in learnine the orinciales and the aoolications of electronic interfaces in wireless chemical data communication. A preliminary project that attempts to satisfy this interest has been carried out by our students. Data obtained from an iodine clock reaction were transmitted in the form of electromannetic waves to an Apple I1 microcomputer that had been connected to a wave receiver through an interface. The computer then calculated the order of the reaction. In order to make the svstem as inexpensive as possible, a minimum number of materials were &ed. The items involved included a phototransistor, a radio transmitter, and servo, all of which can be readily purchased from model or hobby shops. The output of the phototransistor was connected to a commercially purchased radio transmitter (Fig 3). The trimmer was set such that the output of the phototransistor under maximum ore-set lieht intensitv was eaual to that of " the maximum transmitter trimmer soltage. As a result, the trimmer of the ~hototransistortook over the function of the transmitter trimmer in the radio control. We used the signal intended to drive the motor in the servo as the inputio the receiver interface. The range of the input was e4V. The IC74CS14 interface used for this work was connected to one channel of the receiver as shown in Figure 4; neither amplification nor attenuation of the signal was necessary. In combination with the laboratory location where the preliminary transmission work was done, our system proved virtually impervious to interference that could
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