UOP 211-79

This method is for plant control analysis of used refinery caustic solutions. It is especially useful for solutions containing Merox catalyst used for the extraction or sweetening of mercaptans. Two characteristics of a used caustic solution are determined; namely, total alkalinity and the caustic consumed by the presence of mercaptan. Free sulfur and polysulfide sulfur may interfere with the test. Hydrogen sulfide does not interfere.