The Sedimentation Volumes of Soils from Certain Major Soil Groups

IN some investigations of the physical and chemical characteristics of soils from the erosion experiment stations of the U. S. Dept, of Agriculture, Middleton and Byers ( i ) 3 and Middleton, Slater, and Byers (2) reported measurements of the settling volumes of soils. They found that when soil was shaken with an excess of water and allowed to stand 24 hours, the sediment occupied a definite and reproducible volume which was related to the moisture equivalent, mechanical composition, and other physical properties. They also found that the settling volumes of the extracted colloids of these soils depend upon certain chemical characteristics of the soil material. Smolik also reported determinations of settling volumes, but failed to find any relationship between the settling volumes of the soils and any of their other physical or chemical properties. In the present investigation measurements were made of the volume of sediment formed when profile samples of a group of diverse soils were allowed to settle in water and in xylene. Duplicate soil samples were run in a centrifuge and the sedimentation volumes under the influence of centrifugal force were measured, using both water and xylene. The sedimentation volumes of the colloids extracted from these profile samples were determined employing both water and xylene.