Abstract
The effect of L-alanine on dispersion and coagulation of ferric hydroxide sol was investigated by optical measurement of the coagulation rate. Ferric hydroxide sol was prepared by pouring a ferric chloride solution into boiling water. A small quantity of sodium hydroxide solution was added to the sol, and the coagulation rate was monitored based on the change in turbidity with time. The turbidity change vs. pH showed a maximum at the point of zero charge, which was obtained by electrophoretic mobility measurements of the ferric hydroxide sol particles. The maximum of the turbidity cnange vs. pH curve shifted towards the iso-electric point of L-alanine by the addition of this agent. The change of the point of zero charge was also observed by electrophoresis when L-alanine was added to the sol. L-Alanine was found to be an effective dispersing agent for ferric hydroxide particles at pH 2-8, and its effectiveness was enhanced by the presence of sodium chloride.
