A FLOW MICROCALORIMETER FOR MEASURING THE HEATS OF MIXING OF BINARY LIQUIDS BY A CONTINUOUS PROCESS

In order to measure heats of mixing or heats of dilution for many solutions by a continuous process accurately, a twin conduction type flow microcalorimeter has been constructed, improving the design of the same type of calorimeter reported previously. The thermal stability of the heat sink was enhanced by enlarged contact area of the main heat sink block with a thermostated water bath. Mixing efficiency of the mixing cell and the stability of the base line were improved by the use of a new mixing cell having a long mixing zone and symmetrically arranged sample and reference cells. Waiting time for establishment of thermal steady state was also reduced by sandwiching each of the cell by a pair of wide thermopiles plates and a pair of sub-blocks. Heats of dilution of aqueous urea solutions were measured by a continuous process, and results obtained well agreed with accepted values by Gucker et al. The accuracy and thermal resolution in this calorimeter were estimated to be less than 0.05% and 3 muJ.s-1.