Abstract: A method and an apparatus for controlling the concentration of oxygen and pH of a medium during a bioreaction process in a vessel. The method and apparatus are particularly adapted to a fermentation process. A dissolved oxygen sensor generates a signal corresponding to the pH of the medium and a dissolved oxygen sensor generates a signal corresponding to the dissolved oxygen in the medium. A valve mechanism selectively applies air, N.sub.2, O.sub.2 and CO.sub.2 to the medium. A controller produces a control signal for controlling the operation of the valve means so that a substantially fixed volume of gas consisting of one or more of air, CO.sub.2, N.sub.2 and O.sub.2 are added to the fermenting medium during a period of time. The controller determines in response to the dissolved oxygen and pH signals, the amount of CO.sub.2, O.sub.2 and/or N.sub.2 required to effect dissolved oxygen and pH correction. The controller further adjusts these determined values to compensate for the displacement of the CO.sub.

Abstract: An apparatus and method are described for automatically correcting drift in automatic titrations, such as coulometric titrations of water. An endpoint detector provides a signal indicative of the state of the titration mixture and the detector signal is monitored by two comparators, responsive to titration mixture states on opposite sides of the endpoint and connected to means for controlling forward and back titration. At the end of a titration, the titration time and amount of titrant are stored in memory elements, and circuitry including an array of gates monitors the comparator signals during two post titration time periods to determine both the direction and rate of drift, and to correct the titration results for the amount of drift detected.