NATURE AND PROPERTIES OF YAMAGATA BENTONITE

Abstract

The following are the results of my study on a certain yellow species of the Yamagata bentonite.(1). A water imbibing mass at the swelling equilibrium (25.0°C) contains 0.359g of dry clay per 100g of the mass, and its calculated values of sp. volume and swelling ratio are 0.980cc and 1:73.0 respectively.(2). On adding ample water an abnormally rapid swelling is observed on the surface of a dry or partially imbibing clay mass. Let us call the swelling “surface swelling”. The surface swelling, with some quickness, takes an equilibrium which correspond to a terrace, nearer to the origin, on the time-swelling curve, and leaves a gelatineous thin film on the surface, a film completely covering the surface, insists against further penetration of water. A time interval to reach the equilibrium of the surface swelling becomes shorter both with the increase of initial distribution density of surface particle and with dryness or concentration of the mass of clay, and yet the gel film thickens with the shortened time interval just mentioned.(3). A film of bentonite, 0.1-0.05mm thick, does a directional swelling, viz., at the swelling equilibrium the ratio of swelling is 1:39.0 in the direction of thickness and 1:1.37 in that of spreading.(4). The swelling velocity of film, in both directions, may well be denoted by the following equation:di/dtk(i∞-it)Here, it is a ratio of swelling at any time interval t, and i∞ another at infinite time, k being a constant of proportionality. This equation is quite the same as that of simple chemical reaction velocity.(5). On considering a mechanism of film formation we can infer a type of bentonite micelle model. The model has a layer structure which can be exemplified by a alternative film layer of Al-hexite an Si-hexite, and it has almost the same structure as the crystal structure of kaolinite or some base-exchange type clay.