An AutoAnalyzer method has been developed to determine free alkalinity or acidity in soap by use of a mixed cresol red-phenolphthalein indicator solution and by measurement of the color developed at 550 m~. An internal standard or reference solution is used consisting of a soap solution which has been adjusted to represent neutrality. The method was applied for 0 to 0.10% free alkalinity, calculated as sodium hydroxide, and for 0 to 0.50% free acidity calculated as oleic acid. Attainable precision of the method (95% confidence limits) in the ranges explored was found to be --+0.0025% for free alkali and _+0.05% for free acidity.