Soil Research Soil Research Society
Soil, land care and environmental research

Dispersion of calcium clay

P Rengasamy

Australian Journal of Soil Research 20(2) 153 - 157
Published: 1982


The dispersion of samples of calcium-saturated soil clay, calcium illite, and calcium bentonite was compared with the dispersion of sodium clays. Each clay was first freed of electrolytes, one sample of each being dialysed with water and a second washed with ethanol. All samples were then dried at 105°C. The dialysed calcium clays did not disperse in water even after a week, but dispersed spontaneously when immersed in water immediately after they had been remoulded. The calcium clays that had been washed in ethanol dispersed spontaneously in water to the same extent as dialysed sodium clays. After the samples were equilibrated at a fixed relative humidity, the water uptake in ethanol-washed calcium clays was twice that of corresponding dialysed calcium clays but similar to the dialysed sodium clays. A mechanism of hydrogen bonding in dry calcium clay is proposed which includes exchangeable calcium, water molecules, and the exposed oxygens of the clay layers. The replacement of water molecules in the bond by ethanol weakens the bond and leads to swelling and dispersion of the clay.

© CSIRO 1982

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