An Automatic Titrator for Student Use Potentiometric titrations are an integral part of analysis courses and are widely utilized. The high east (>$5000) of automatic titrators make them unavailable to many schools with the result that students must then use the slow, tedious method of recording potentials as a function of buret readings. We have produced a very aceeptahle automatic titrator by combining a syringe pump, a pH meter with a recorder output, and a strip-chart recorder. The syringe pump serves as a constant delivery huret, and the pH meter with the chart recorder records the potential as a function of titrant volume. A Sage Model 341 A syringe pump (list price $750 and often discounted by laboratory supply companies) was used for a buret. Depending on syringe size and pump setting, flow rates from 0.092 pL/hr to 13 mllmin are possible. I have found that a 301.111 syringe and a delivery rate of about 1mllminto beconvenient. The titrant is delivered from the syringe to the titration vessel (beaker atop a magnetic stirrer) via plastic tubing that had a small amount of lead wrapped around the delivery end to help keep it in place. The titrant should not be delivered next to the measuring electrode. The following procedure is used: The syringe is filled with titrant, air bubbles are removed, and the syringe is placed in the syringe pump. The pump is turned on until titrant emerges from the plastic tubing and then turned off. The tubing is placed in the titration vessel and the pump restarted simultaneously with the chart recorder. This procedure has produced good, smooth, reproducible titration curves both with aqueous and nonaqueaus systems. I t is easier to standardize this system by determining the ratio of equivalents of standard per chart distance rather than to determine the actual delivery rate of the titrant.
Joseph E. Byrne Norwih University Nathfield, VT 05663
Volume 61
Number 9
September 1984
829
