HYDRATION CONTROL OF MONTMORILLONITE AS REQUIRED FOR ITS IDENTIFICATION AND ESTIMATION BY X-RAY DIFFRACTION METHODS

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Abstract
A method is presented for providing the necessary control of hydration of montmorillonite for x-ray diffraction analysis. Fine clay (particles < 0.2 [mu], in diam.) is fully base-exchange saturated with Ca, and then washed successively with water, absolute methanol, and benzene. The clay is then suspended in a ternary soln. of benzene, ethanol, and water, the composition of which is such as to provide true soln. but near-saturation with respect to water. Benzene is added to the suspension, resulting in setting free a water-rich 2d phase in finely divided form throughout the suspension so that it is sorbed uniformly by all of the clay. The amt. and composition of the ternary soln. in which the clay is suspended, and the amt. of benzene later added, are suitably adjusted so as to expel the required quantity of water (50% of the dry wt. of the clay) and still maintain a suspension medium which is largely benzene. Most of the supernatant liquid is decanted, and the clay dried under controlled conditions (30[degree]C and 65% rel. humidity). The clay thus treated dries to an incoherent powder, somewhat softer than that resulting from drying the clay from anhydrous benzene, in which condition it readily reaches equilibrium at any desired rel. humidity. A portion of the dried clay is mounted in the receptacle so as to give a definite volume-wt. for x-raying, and then is humidified for about 15 hrs. in a desiccator maintained at 92% rel. humidity and later x-rayed at this humidity. Special equipment for this humidification is described.

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