This document describes the procedure for determining the free swell index of soils. The test involves taking a soil sample, drying it in an oven, sieving it to remove particles larger than 425 microns, and placing 10g of the remaining soil in each of two 100ml flasks. Kerosene is added to one flask and distilled water to the other, and both are stirred and allowed to settle for at least 24 hours. The free swell index is calculated as the percentage increase in volume of the soil-water mixture over the soil-kerosene mixture. At least three readings should be taken and averaged to obtain the final result.