In this study the dissolution of Colemanite in aqueous acetic acid solutions was investigated in a batch reactor employing the parameters of particle size, solid-to-liquid ratio, and temperature. It was found that the dissolution rate increases with increasing temperature and decreasing solid-to-liquid ratio and particle size. The most effective parameter was particle size with a power of -1.420 after temperature and solid-to-liquid had less effect than the other parameters. The conversion rate increased up to 3.365 M acid concentration and then decreased with increasing acid concentration. No important effect of stirring speed was observed. The activation energy of the process was determined to be 51.490 kJ mol(-1). It was determined by graphical and statistical methods that the reaction fits a model in the form of -ln(1 - X) = kt. The following semiempirical mathematical model, which expresses the process well, was established: -ln(1 - X) = 56 664(D)(-1.42)(S/L)(-0.270) exp(-6193.0/T)t, where X is the conversion fraction, D the particle size, S/L, the solid-to-liquid ratio, and T the reaction temperature.