The microcalorimeter has a measuring cell to contain culture medium for the experiment and an identical reference cell. The cells are housed in a thermostatically controlled, thermally insulated block of material, esp. metal, which is a good heat conductor. Each cell has a multi-thermocouple temp. detector. Throughout an experiment, the head space above the culture medium in the sealed cell is filled with a gas of controlled compsn. A very low flow rate of the gas, at a temp. close to that of the block, is passed through the head space from a source outside the caldrimeter. Within the cell, the experiment takes place in controlled atmos. conditions. The head space is pref. connected to the exterior of the thermocouple by two pipes, one for inflow and the other for outflow of gas. Each cell pref. takes the form of a shallow, cylindrical dish which rests upon the temp. detector. Through the top sealing cover of the cell are passed inflow and outflow pipes for gas, drive shaft for rotary agitator and graduated syringe(s) for injection of reagents. The gas can be air for aerobic cultures, an inert gas to purge out gaseous cell prods. such as H2, H2S, methane etc., or CO2 for the study of photosynthesis.
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