Experimental data on the rate of formation of propane hydrates were obtained using a particle size analyzer capable of detecting particles with diameters as small as 0.6 nm, while operating in a closed loop system. Experiments were carried out at temperatures around 274 K and pressures between 315 and 340 kPa in a semi-batch stirred tank crystallizer. The experimental data were analyzed using a newly developed kinetic model based on crystallization theory and as a result, the actual reaction rate constant for propane hydrate formation was successfully determined. A value of 2.15 x 10(-7) m/s is reported at 274.2 K, while it was found that the dissolution rate of propane at the vapor-liquid water interface was enhanced by a factor of five during the growth stage, compared to the value obtained during typical solubility experiments. (c) 2008 Elsevier B.V. All rights reserved.