Major Components an MS-DOS microwmputer, a 12-bit analog to digital w.nverter interface card (Real Time Devices AD500), a custom-built stepper motor interface card, a stepping linear actuator motor (Hurst 3602-0011, s 50-mL glass hypodermic sJlinge, a custom-builtmetal mounting frame for bath the stepping actuator and the syringe,and an ion meter with an analog output (Orion 811). Hardware An overview of the equipment employed in this project is shown on Figure 1. The students can vary the volume and time delay in this feedback loop in order to record the most accurate titration curve. ARer the initial addition of base (or acid, the pro~amfollowsa three-step cycle.Īn MSDOS Microcomputer Controlled Titration SystemĮdited bv JAMES P. Gorithm imitates the manual technique of titration where the measurements are widely spaced when the slope is shallow, but the measuremenk a c very close in reglo-m of steep slope. Schematic diagram of the titration system. Instead of evenly spaced measurements, this method gives a high density of data points near the equivalence point where the slope is steepest. In this experiment the computer is employed to wntrol the addition rate of titrant based on the change in pH of the analyte system. This experiment can be used to demonstrate the principles of computer interfacing, motion control, and feedback wntrol. Feedback control of the titrant volume increments was not employed in these previous studies. Long ( 4 )and Vitz (5) also have presented stepper motor-based titrant pumps. (21, and Cornelius and Norman (3) have presented full-scale titration experiments using the PDP and Apple I1 computers. Similar stepper motorbased titration experiments have been presented in the past. This paper reports a relatively inexpensive project for an automatic titrator using a n MS-DOS microcomputer, where software controls the progress of the experiment through the rate of titrant addition. Experiments that employ the microcomputer to control a procedure directly give students a much greater breadth of experience than passive data acquisition experiments. Laboratory microcomputers have bewme powerful tools for experimental chemists, and this trend will wntinue as these wmputers become more affordable. contml, and analysis during experiments has b&me inireasinelv i m ~ o r t a n to t the curriculum of the instrumental a a s i s course. The use of microwm~uter-baseddata acquisition. Anjo California State University Long Beach.
The computer waits a reasonable delay time for mixing of the reagents and electrode stabilization.ĭennis M. The pH is measured, and the slope is calculated relative to the previous addition The program determines the amount of base to add dependent on the slope, and this amount of base is added. Computer series, 136 Leiv Jonn Stangeland Telemark lngenisrhsgskole 3900 Porsgrunn, Norway
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