Colloid Chemical Researches on Suspensions in Pharmacy. I. On Thixotropy in Vegetable Oil-Aluminum Stearate System

Abstract

1. By employing the concentric cylinder method, rheological studies were made both on the thixotropy of the peanut oil-aluminum stearate system, the most commonly used base for penicillin injection, and also on the castor oil-aluminum stearate system for the sake of comparison. 2. Peanut oil and castor oil containing no aluminum stearate showed the Newtonian flow. The mechanical behaviours of the oil-aluminum stearate system were expressed by mechanical models. 3. The mechanical models of the system containing aluminum stearate (up to 2%) in peanut oil were as follows. Immediately after stirring, the sample behaves as a pure viscous flow (Newtonian flow), whose viscosity coefficient was very high compared to the oil containing no aluminum stearate. This model became the Maxwell model with Newtonian flow and then it turned into the Maxwell model with non-Newtonian flow in the course of time. On the other hand, the model for the castor oil system containing aluminum stearate (up to 2%) was always Newtonian flow, and neither elasticity nor non-Newtonian flow was observed in the course of time after-standing of the sample.