THE MECHANISM OF THE HYDRATION OF CALCIUM OXIDE

Abstract

Three samples of calcium oxide, designated as A, B, and C, were prepared from calcium carbonate labelled with calcium-45. A was heated to constant weight at 700 °C.; B was heated an additional three hours at 1400 to 1550 °C.; and C was heated six hours at the same temperature. The samples were hydrated in a supersaturated lime solution at 21 °C., the development of activity and the changes in concentration of the solution being determined. The activity entering the solution accounted, according to theory, for the following percentages of the samples passing through the solution during the hydration: A, 27%; B, 57%; C, 94%. These results indicate that sample C ("dead-burnt" lime) hydrated by a "through-solution" mechanism, but that A and B either hydrated partly according to some other mechanism, such as a vapor phase process in the pores of the particles of lime, or the calcium ions failed to reach the bulk of the hydrating liquid before precipitation as calcium hydroxide.