The difference in pKa values of acetemimophen and phenobarbital permits differentiation of mixtures containing these drugs. Titrations are performed nonaqueously using tetrabutylammonium hydroxide as the titrant. End-points were determined potentiometrically using a platiniuö-calomel electrode system. Methylisobutylketon and methylethyl keton were evaluated as solvent for the titration. Keywords :