Experimental data on the rate of carbon dioxide hydrate formation in a semibatch stirred-tank reactor was obtained using a particle-size analyzer capable of detecting particles as small as 0.6 nanometers in a closed-loop system. Experiments were carried out at temperatures between 275.3 and 279.4 K and pressures ranging from 2,014 to 3,047 kPa. The reaction rate constant of CO, hydrate formation was determined using a newly developed kinetic model independent of the dissolution rate at the vapor-liquid water interface. The average reaction rate constant determined experimentally was found to increase with temperature following an Arrhenius-type relationship, from 1.8 x 10(-8) m/s to 1.8 x 10(-7) m/s, over the 4-degree range investigated. Similarly, the reaction rate constant calculated from a population balance varied from 1.4 x 10(-8) m/s to 1.7 x 10(-7) m/s over the same temperature interval. The initial number of hydrate particles was calculated using the mole fraction of the gas hydrate former in the bulk-liquid phase at the onset of hydrate growth rather than the equilibrium solubility. The cumulative relative scattering was also compared to the derived count rate to determine whether or not the number of hydrate particles remained constant during the hydrate growth experiment. (C) 2008 American Institute of Chemical Engineers AIChE J, 54: 2964-2970, 2008