A study of the validity of the ilkovic and other standard direct and alternating current polarographic equations at short drop time

A. M. Bond, R. J. O'Halloran

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Both short drop time ac and dc polarography, which permit fast scan rates and increase the polarographic time scale several orders of magnitude, are potentially extremely valuable techniques in many kinetic, analytical, and electrochemical investigations. Early work utilizing short drop times indicated that standard polarographic equations were inapplicable to such measurements, and the use of drop times below 2 sec has been generally discouraged in the literature. Recently, however, data have been obtained in the millisecond drop time region which indicated that much of the standard theory can in fact apply in this drop time range. The present study reports an investigation of short drop time polarography in an endeavor to resolve apparent anomalies currently existing in the literature, and to overcome possible unjustified discrimination preventing the much wider use of a valuable technique of polarography. Results demonstrate conclusively that the presence of the short drop time itself does not lead to a breakdown of conditions for which standard ac and dc theories were derived. If short controlled drop times are obtained by mechanically knocking the capillary then the short drop time experiment is found to be critically dependent on the theory applicable to the natural drop, from which the short controlled drop is derived. In obtaining the short controlled drop time, the flow rate of mercury is essentially unaltered. On the other hand, if short drop times are obtained by gravity control, it is confirmed that the standard theory no longer applies, because the flow rate of mercury becomes too large, and it would appear that it is variations in this parameter, rather than the drop time which has caused many of the difficulties encountered in the past.

Original languageEnglish
Pages (from-to)915-922
Number of pages8
JournalJournal of Physical Chemistry
Issue number7
Publication statusPublished - 1 Dec 1973
Externally publishedYes

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