Some measurable solution properties related to the reactant concentration, such as light density, conductivity, electromotive force, and pressure, are usually used to measure the rate constant of a chemical reacton. In this paper, the effective permittivity of a solution, where the acetone iodation reaction is carried out, has been measured and proposed to be used to calculate the rate constant of reaction. The rate constant is compared with the result calculated by using the conductivity. Both of them are in satisfactory agreement and approach the theoretical values.