A test and calibration process for microcalorimeters used as thermal power meters

A test and calibration process for microcalorimeters is described. The method has been developed with particular reference to instruments used for measurements of thermal power produced by suspensions of living cells. The process investigated is the hydrolysis of triacetin in imidazole/acetic acid buffer. The power levels are regulated by changing the buffer composition. The power will decrease slowly and very nearly linearly with time. Five test solutions, power levels 7-90 microW X ml-1, have been characterized at 37 degrees C and one of them at 25 degrees C (13 microW X ml-1). The power values for these reaction mixtures can be accurately calculated (+/- 0.5%) as a function of time during extended reaction periods, about 20 h or more.