modern polarographic methods helmut schmidt de schmidt helmut (1 résultats)

Hardcover. Etat : Good. Dust jacket condition: None. Solid retired library book with usual library markings; else VG. Text free of underlining, writing and highlighting. From the Foreword: The polarographic method developed about 40 years ago by Heyrovsk is still used with undiminished success; though it is unchanged in principle, numerous modifications of the classical method, some trivial, others important, have been published in recent years. It seems, therefore, timely to discuss these new procedures, to point out their advantages and disadvantages with respect to established polarographic methods, and, insofar as it is at present possible, to outline their significance for analysis and the solving of scientific problems. The improvements striven for in these new methods have essentially the following intent: 1. Increase in Sensitivity. Although in recent years there has been a considerable advance in the development of apparatus, nevertheless the possibilities of modern amplifier and recording techniques have not by any means been fully utilized. The reason for this is that any further increase in the sensitivity of apparatus is pointless as long as over-all sensitivity is limited by the reaction which is being investigated. As is well known, this limitation of sensitivity is controlled in polarography by the capacitance current. For the build-up of the electrical double layer at a constantly maintained voltage, the increasing surface of the growing drop requires a transfer of charge, which is greater the further conditions are removed from the zero potential of the dropping-mercury electrode. (With an applied alternating-current voltage there is in addition an alternating-current charging current.) If the faradic current is of the same order of magnitude as the capacitance current, or is less, then its exact determination is impossible. Attempts to compensate the capacitance current were made from quite an early date, and from them a necessary improvement, particularly for analytical purposes, was achieved. . . .