The ratio of ice salinity to brine salinity, k, has been measured at temperature gradients up to 1.3 °C/cm. The data obtained have been found to fit the empirical equation k = 0.1 + 0.293 dt/dx. This equation was used in a digital simulation of the freezing process and the results were compared with data obtained in field experiments in a temperate climate. The computed ice salinities were within 25% of measured salinities at any particular level in ice having a horizontal c axis, and the computed average ice salinity was within 5% of the actual average ice salinity.Under the climatic conditions of the experiment this equation was found to be more accurate than an equation derived by Weeks and Lofgren.