Knowledge of the compounds of hydrated calcium silicate and their equilibria is important in cement technology and in regard to the use of siliceous minerals in cement.Hydrated calcium silicate is gelatinous at room temperature, regardless of method of preparation or time. However, the units of physical structure may be well-organized and definite, since X-ray analysis has shown that most inorganic gelatinous or amorphous materials are in reality crystalline, while all are crystalline (to X-rays) whose atoms or radicals are dior monovalent.1 A diffraction pattern has in fact been reported by Chassevant2 for Paul S. Roller and Guy Ervin, Jr.Vol. 62 coagula.7,8 A third method of experiment consists in precipitating hydrous calcium silicate and treating this with lime water. Because in this method the initial solid phase is a hydrous compound more or less closely related to the final products of equilibrium, a comparatively rapid approach to equilibrium would be expected. This in fact has been realized in the present work.Chemical analysis has in the past frequently neglected the correction due to dissolved silica.The association constant, solubility product constants, and one of the ionization constants, were calculated to a known precision. A high tendency toward association is evidenced.College Park, Md.

have been made is that such linings should give protection under any condition where iron hydroxide tends to precipitate. Thus in tuberculating water such pipe is excellent. Cement-lined pipe has been found good in other water, however-as, for example, in salt water and sulfur water, where the tendency toward tuberculation is not so marked.

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In reaction between two phases, two factors a priori determine the overall measured rate of reaction. The first is the rate of chemical reaction at the interface; the second is the rate of transport of reactant, or product of reaction, to or from the interface. For heterogeneous reaction in which one or both phases are fluid, the transport takes place between the interface and the point of measurement.In the present work, dealing with the fluid-fluid or fluid-solid heterogeneous reaction, a quantitative relationship is derived for the measured rate as a function of the chemical reaction rate and rate of physical transport. No arbitrary postulates as to mechanism are made. The results follow in the first place from a solution of the diffusion equation with chemical reaction at the interface constituting one of the boundary conditions. In the second place, diffusion as a mode of transport is generalized to include transport due to stirring or other type of agitation. THE NERNST THEORYIn 1904, Nernst (21, 2) proposed a theory of heterogeneous reaction , which has been referred to widely. In this theory certain assumptions are made as to the chemical and physical factors of the liquid-solid heterogeneous reaction. On the chemical side, reaction is supposed to be in-