Conductivity studies of suspension systems in different states of aggregation.

The electrical conductivity effects of dispersed, coagulated, and flocculated systems were investigated using sulfamerazine powder, an insoluble, hydrophobic drug to prepare the suspension systems. For the dispersed systems, a peak in conductivity was observed at a drug concentration between 5 and 15%. The critical coagulating concentration was defined as the concentration of drug at which a maximum in specific conductance was observed. At this concentration, a maximum number of charged particles were in the system. Coagulated suspensions showed higher conductance values than the dispersed systems at equivalent concentrations; however, the critical coagulating concentration value appeared to be the same. For flocculated suspensions there was an increase in conductance with drug concentration with no perceptible peak conductance value.