Ethylene Glycol Monoethyl Ether for Determining Surface Area of Silicate Minerals

Total surface area is a fundamental property of layer silicates, and it has been used as a cri-terion for identification. Early methods for de-termining surface area used nitrogen or ethane gas and were based on the principle that solid materials will adsorb a monomolecular layer of the gas at a particular pressure (4, 6). Dyal and Hendricks (6) introduced a method for deter-mining surface area with ethylene glycol. Their method has been adapted to determining surface area of soils and soil minerals (2) and, although it is not an equilibrium method, much useful information has been provided by its use. The Dyal and Hendricks method has been modified to include a source of free ethylene glycol or an ethylene-glycol-solvated material to control the vapor pressure of the ethylene glycol at the adsorbing surface (1, 10, 13). Several workers have used glycerol successfully to de-termine surface area of both layer silicates and soils (5, 7, 9, 12). Both ethylene glycol and glycerol molecules are polar, and at present both materials are in use. Other methods in limited use include application of the B.E.T. theory (4), using ethylene dibromide (8) and the adsorption of organic molecules from solutions (3). All surface-area methods are rather tedious and time-consuming. A more rapid technique to provide surface area data with precision equal to or better than present methods would be use-ful. This paper reports the use of ethylene glycol monoethyl ether (2-ethoxyethanol) (hereafter referred to as EGME) for determining the total surface area of three reference-layer silicates. Results are compared with those obtained from the ethylene glycol method proposed by Bower and Goertzen (2).