PRODUCT DISTRIBUTIONS IN THE CO2-NH3-H2O SYSTEM FROM LIQUID CONDUCTIVITY MEASUREMENTS

The objective of this work was to illustrate how liquid conductivity measurements could be used to provide information about the extent of ionization and the amounts of the various ionic products that are formed in the liquid phase in the CO2-NH3-H2O system. To accomplish this, pressures and liquid-phase conductivities for the CO2-NH3-H2O System were measured at 25-degrees-C and over a range of pressures and concentrations. In order to acquire the desired information from bulk conductivity measurements, calibration curves were established from measurements with several potassium salts. These curves, in conjunction with the experimental conductivity, allowed the (approximate) determination of both the concentration of the NH4+ ion and the distribution Of CO2 between singly and doubly charged ions. Comparison to the predictions of two existing models for the CO2-NH3-H2O system showed that these models underpredicted the concentration of the ammonium ion. This suggests that correct predictions of the vapor-phase compositions and pressures by a solution model do not guarantee that the description of the liquid phase is correct.