Measuring the diffusivity of various substances in cortical bone is in general difficult. For instance, making use of micro computed tomography requires agents that can be separated from bone, blood and other substances that exist in cortical bone. Here a more easily accessible method is presented. A series of cortical bovine bone samples were put in a saturated solution of potassium chloride for a time period that was long enough for the samples to be regarded as saturated. The samples were removed from the solution and moulded in polyester leaving only the radial directions open. In the next step, the bone samples were put in distilled water and the conductivity of the water was registered over time. An analytical model fulfilling Ficks law was introduced and by means of Kalman filtering an estimation for the diffusion coefficient of potassium chloride in bovine bone is presented.