Document Type


Subject Area(s)

Chemical Engineering


A simple steady-state model of a diaphragm-type chlorine/caustic cell in which the diaphragm is divided into two regions by a homogeneous acid-base reaction is presented. The location of the reaction affects significantly the caustic yield and effluent concentration. The model is used to predict the location of this reaction as a function of the operating variables, the physical constants, and three measurable properties of the diaphragm. These measurable properties are the MacMullin number or resistivity ratio of electrolyte-filled diaphragm relative to the electrolyte, the Darcy's law diaphragmpermeability, and the diaphragm thickness. The model is used to predict a maximum in the relationship between the caustic yield and caustic effluent concentration. The model predictions are compared with experimental data by using parameter estimation techniques to determine the diffusion coefficients of hydroxyl and hydrogen ions and the average specific conductivity of the electrolyte within the diaphragm during operation of the cell.