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Chemical Instrumentation Edited by GALEN W. WING, Seton Hall UnivenRy, So. Orange, N. J. 07079
These orticlea are inlmdcd lo rn fhe reader8 O ~ T H I SJOURNAL by callinp allenlia lo new developmmls in the fhemy, dew,m awilability of chemical laboratmy imtrumentalh, m by premting useful imighk and wplawliund of lopica that are of praclicol impmtcncc lo those who use, m k w h the uae of, modem iMhmtmtotim and inufrumental lechniqua. Thc editor inmle8 cmreapondence from prospective contribulora.
chronopotentiometry, and (3) as a potentiostat for polarography, cyclic voltammetry and related methods. The Electroscan-30 ha9 a built-in, highimpedance strip-chart recorder capable of half-second pen response even with 2 megohms source resistance. The chart drive can he reversed for cyclic voltammetry.
Prhcefon Applied Research Corp.
P.A.R., in 1968, introduced a multiple purpose instrument designated the Model 170 Electrochemistry System (Fig. 2) ( 9 ) . The desieners aoint out that the instrumentaiion for nearly all electrochemical techniques can he resolved conceptually into three portions: firstly, a function generator and control element which applies the required pot,ential or current to the cell; secondly, a circuit to measure the desired quantity; and thirdly, a data-processing system to provide a snitahle signal to the read-out device. The P.A.R. instrument panel is power suppli&. Each plug-in unit prolaid out with this logic in mind, conditionvided the signal generators, feed-hack neting controls grouped to the left, measuring works, range-switching, and other circontrols in the center, and controls for cuitry needed to program the amplifiers data processing to the right. The P.A.R. for the particular requirements of one instrument employs sophisticated operaelectrochemical method. A very similar tional amplifier circuitry as well as digital instrument, developed independently, but loeic. the latter Dartieularlv " in connection following a suggestion by Shain, was dewith' pulse polat~ography. scribed in detail by Propst (6) in 1964. Foiu innovations are especially deservLauer, Schlein: and Osteryoung (3) ing of comment. ( I ) An electromechsnicd chose to program their amplifiers by timer is arranged to dislodge drops of multiple switching. Their indnlment, mercury from a palarographic capillary with seven amplifiers, incorporated twelve a t 0.5, 1, 2, or 5 sec intervals. Added switches and six relays. I t was designed circuitry then makes it possible to measure particularly for fast, controlled-potent,id the dron current durine.. a . medetermined sweeps with simultaneous integrat,ion of and ex&ly reproducible period just precurrent, hence is somewhat mare specialceding fall-off. ized than some experimenters might (2) A summing amplifier is utilized to wish. apply excitation to the cell without ikelf I 4 ron*trorrrd uht the excitation signals. The :tna.t~ntr~rl 10 H v e r w ~ l cHI.BI
