The techniques of a-c and d-c rapid polarography employing short controlled drop times and fast scan rates of potential are discussed in detail. Particular emphasis is given to comparing the methods with conventional polarography in electroanalytical applications. The shapes and main characteristics of both a-c and d-c polarograms are essentially the same as in conventional polarography. Any differences encountered generally arise from the different time scales of the two techniques. Reversible, quasi-reversible, and irreversible electrode processes are considered. In analytical applications, the rapid methods are superior to conventional polarography because of the considerable time saving gained from the fast scan rates of potential. The reproducibility is also marginally better. In fundamental studies, such as in the characterization of electrode processes, rapid polarography is also shown to be particularly useful. The analogy of behavior akin to a streaming mercury electrode is considered, as are other phenomena and characteristics introduced by having short controlled drop times. It is concluded that the technique could be given wider usage than presently accorded.One of the disadvantages of conventional polarography compared with other analytical methods has always been that the natural drop times of the dropping mercury electrode (DME)musually between 2 and 8 sec--necessitate reasonably slow scan rates of potential, and the time required for recording a polarogram is correspondingly long. Scan rates of potential must be slow for two major reasons: (A) to avoid violating the constant potential-current conditions assumed for theoretical purposes, and (B) to provide a high degree of precision of measurement. Each drop represents one data point on the current-voltage curve, and especially over the steeply rising portion of a d-c polarogram or around the peak or summit potential of an a-c polarogram, a large number of data points is necessary. Obviously, the faster the scan rate, the fewer data points on the graph and this results in a decrease in precision. Thus, even if the theoretical constant potential-current requirement did not need to be met, there would still be an excellent practical reason why the scan rate cannot be increased beyond well-defined limits when natural drop times are used.In electroanalytical methods with stationary electrodes, such as the hanging drop mercury electrode, platinum electrode, glassy carbon electrode, etc., fast scan rates of potential are used routinely. The theory for stationary electrode voltammetry includes terms for the scan rate of potential and so restriction given as (A) above for polarography does not apply, nor does that given as (B), because a continuous currentvoltage curve is obtained. Similarly, with streaming (mercury) electrodes, no restriction is placed on current-voltage curves. However, although voltammetric methods may be used with considerable time saving, they have several well-established difficulties and disadvantages compared with the polarographic...