The determination of clay in heavy soils

Abstract

1. The Sudan method for clay determination worked out by Dr Beam in 1911 has been critically examined and compared with the methods in general use in England and America.2. The essential points of the method lie in (a) the use of sodium carbonate instead of ammonia as the deflocculating agent, and (b) the use of a camel-hair brush for puddling the clay. It differs from the English (and resembles the American) method in that no preliminary acid treatment is used, the height of the sedimentation column is 10 cms. and the time of subsidence 8 hours.3. It can be applied to a sedimentation or centrifugal process: the results agree well with each other and with those obtained by the American method.4. When modified by inclusion of acid treatment, by increasing the time of sedimentation from 8 to 24 hours and reducing the height of the column to 8·6 cms., the results agree well with those obtained by the English method.5. Treatment with acid either in the preliminary operations or for deflocculating clay suspensions may lead to uncertainty in the results in some cases as it causes loss of “clay” by solution.6. The Sudan sedimentation method can be carried out in about one-eighth the time required for the English method, and the centrifugal in about one-third the time required for the American. For general use the sedimentation method is preferred as requiring less attention.