No abstract

We have built a titration calorimeter that is suitable for measurements on colloidal suspensions as well as more conventional chemical reactions in solution. This calorimeter has been used for investigation of a number of ion exchange reactions involving kaolinite and montmorillonite clays. Results of these measurements have led to cation exchange capacities, to enthalpies of ion exchange reactions, and also to equilibrium constants for some of these same reactions. These calorimetrically determined cation exchange capacities and equilibrium constants agree well with corresponding quantities obtained by way of conventional methods based on chemical analyses. It has been demonstrated that titration calorimetry is a useful and convenient method for investigation of ion exchange in clays.

An investigation has been made of the kinetics of hydration o f tricalcium silicateat several temperatures in a large excess of water in the presence of various added ions. The rate data have been interpreted by a reaction mechanism which involves: (a) the first order hydration of tricalcium silicate to form an intermediate product, 1.5Ca0.Si02, which can react by two pathways, (b) the direct first order decomposition of intermediate, 1.5Ca0.Si02, to form lime and silica or (b') complexing of intermediate with silica and subsequent decomposition to form lime and silica. This reaction mechanism predicts the rate of production of base during the hydration. The effect of various added ions is interpreted in terms of the proposed mechanism.Rate constants and activation energies for the various steps in the proposed mechanism are reported.

Carbonate sca1 e d~posits have been determined to be a maJor cause of downhole screen plugging in steam stimualted wells in several L1oydmi nster, Canada heavy oi 1 reservoi rs. Lab experiments and anal yses of produced fluids have identified the most likely mechanism of scale formation, and a simple method of using compositional data to determine whether downhole scaling is occurring is presented.

An investigation has beenmade ofthe influence of p H o n the kinetics of hydration oftricalciumsilicate in a large excess of water. The rate constants increase with increasing hydrogen ion activity (aH+),, in the liquid phase when the (a,,+),, is low; however, as the (a,,+),, is increased further the rate constants become independent of the (a,,+) , , : The results have been interpreted by proposing that the rate constants are proportional to the hydrogen Ion activity adsorbed, , on the solid surface. The Langmuir adsorption isotherm was used to correlate the hydrogen ion act~vity on the surface to the hydrogen ion activity in the liquid phase.Several particle sizes of tricalcium silicate were investigated and a surface area effect is indicated.Canadian Journal of Chemistry, 49, 833 (1971) Introduction Tricalcium silicate, Ca,SiO,, contains calcium (Ca2+), oxide (02-), and silicate (Si0;-) ions (1). When tricalcium silicate is dissolved in basic aqueous solutions, the reaction products are calcium hydroxide and calcium silicate hydrates of various compositions (2). When a large excess of water, 1000:l weight liquid to weight solid ratio, is used the dissolution reaction is complete and may be represented as in eq. 1 with no precipitation of calcium silicate hydrate