Infrared spectrophotometric determination of the alkalinity of overbased petroleum sulphonates

Abstract

A simple, rapid and selective infrared spectrophotometric method was used to determine the alkalinity of the overbased calcium sulphonate additives. The intensities of the absorbance of the bands at 865 and 1180 cm^–1, assigned to the δ_CO3^2– and ν_{as SO} vibrations, respectively, in the same spectrum of the overbased sulphonate sample were measured. The absorbance ratio method was applied as the path length was not known.