Spectrophotometric Determination of Traces of Water in Acetic Acid

During studies on acid-base reactions in acetic acid it became necessary to determine the water content of acetic acid containing approximately 0.001% water. As this is the lower limit for the Karl Fischer method using the visual end point, a 10 times more sensitive method was developed based on the reaction between acetic anhydride and water. The method involves adding acetic anhydride, heating for 90 minutes at 110° C., and determining the amount of unreacted acetic anhydride spectrophotometrically.