A technique for determining the layer structure and content of clay minerals was developed based on the relationship between temperature, and moisture characteristics of clay minerals. Moisture content in standard specimens, prepared by mixing montmorillonite, kaolinite and quartz in various proportions, was determined by measuring weight loss after heating. Based on the results from differential thermal analysis tests, the ignition loss method was found to be widely applicable to clays with montmorillonite and kaolinite as the main components. Dehydration of constituent water occurred at 530℃ and 800℃ in two- and three-layered clay minerals, respectively
