Abstract: There is disclosed a flow through cell assembly that is particularly useful for housing of the sensing cathode of a dissolved oxygen cell. The flow through cell assembly supports the cathode of the dissolved oxygen cell adjacent the upper surface of a through passageway receiving flow of the liquid under investigation and includes a transversely positioned second probe that substantially blocks flow through the through passageway and provides an orifice area of restricted dimensions immediately beneath the dissolved oxygen probe. The dissolved oxygen probe is positioned substantially coplanar with the upper surface of the through passageway to avoid the formation of any air or gas pockets in the flow passageway which could cause erroneous indications on the dissolved oxygen probe. This also allows a high flow velocity across the sensor tip which permits lower volumetric flow rates and a proportionally greater sensitivity of continuous respirometer instrument utilizing the flow through cell assemblies.

Abstract: There is disclosed an instrument probe assembly that is suited for the measurement of a variable of a flowing liquid stream which contains suspension of debris and foreign matter. The instrument probe assembly includes a housing having a closed end for immersion in the liquid with a concavity in the closed lower end having sidewalls inclined at an acute angle to the longitudinal axis of the housing and at least one through opening in a sidewall of the concavity to receive at least one probe member which is sensitive to a variable of the liquid with its exposed surface generally continuous with the sidewall. The probe member assembly is employed with a pH meter that includes a sensing electrode in the concavity with the reference electrode mounted within an annular chamber of the housing and having the reference electrolyte in contact with the liquid through a porous disk which is mounted in the through opening in the sidewall of the concavity.

Abstract: An electrochemical device for sensing the concentration of dissolved oxygen in aqueous liquids is described. The device has a housing with a projecting boss that supports an assembly of the cell cathode and a permeable membrane with a removable retainer means overlying peripheral edges of the membrane and with compressive sealing means to permit facile replacement of the membrane and/or cathode. The cell anode is of expanded form in the shape of a coiled metal wire wrapped about a plurality of spaced posts within the cell chamber. Internally of the chamber is a tubular means which projects above the cathode in juxtaposition to the expanded form anode to provide a well about the cathode which is thereby shielded from accumulation of any precipitate that may form in the electrolyte in the proximity of the anode surfaces.

Abstract: Aerobic fermentation processes which involve mixing an aqueous microbial food medium with a microbial culture are controlled by continuously withdrawing a sample of the microorganism culture and a sample of a mixture of the aqueous food medium and the microorganism culture, directly and continuously measuring a respiration rate of both samples and proportionating the amount of the microorganism culture admixed with the food medium in response to the respiration rate measured to maintain a ratio of the biochemical oxygen demand of the food medium to that of the microorganism culture at a preselected constant value. This control process is preferably used when decomposing wastes such as sewage by aerobic microbial fermentation.