Date of this Version
For a period of approximately fifteen years investigators in the Bureau of Chemistry and Soils have been engaged in the accumulation of scientific data concerned with colloid material of the soil. During this period a large volume of accurate information has been secured which has been published in the form of bulletins and journal articles. So far as the Bureau publications are concerned, but little has appeared concerning theoretical aspects of the composition of the colloid. They have concerned themselves, for the most part, with methods of isolation and estimation, and determination of general physical and chemical characteristics.