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 0.6nm, while operating in a closed loop system. Experiments were carried out at temperatures around 274K and pressures between 315 and 340kPa 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 2.15×10 −7 m/s is reported at 274.2K, 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.