Freeze-drying of soil clays

The crystallization of ice during preparation of soil clays for freeze-drying can cause aggregation of clay particles. This often results in sample loss by the ejection of material in the water vapour stream during sublimation. These undesirable effects are overcome with many soil clays by the addition of ethanol to a concentration of approximately 4% in the suspension before freezing. The structure of the clay body obtained by freeze-drying appears to depend mainly on the particle-size distribution of the clay; a more coherent structure being obtained from finer clays.