The Model 45600 COD Reactor is a 25-well, dry-bath incubator that provides the 150 °C temperature environment required in Hach’s test system for chemical oxygen demand (COD) determinations. In addition to the COD requirements, this model provides features for timed operation as well as temperature adjustment. In the COD digestion mode, the temperature switch is set in the 150 °C position and the temperature is maintained within ± 2 °C constantly. Heater block temperature can be verified by placing a thermometer (not supplied) in the temperature well provided in the block. In the adjustable temperature mode (100 to 155 °C), the instrument can be used for digestion of other samples that require different digestion temperatures. A 2-hour timer is incorporated for applications where timed digestion is desired. When this feature is used, the bell will sound and the unit will shut off at the end of the selected time period. The timer also can be used without the shut-off feature when operating in the infinity mode. The instrument was tested in our laboratory and is in a good state.