This experiment determines two fundamental quality parameters of oils and fats: the acid value (AV), which measures the concentration of free fatty acids formed by hydrolytic or oxidative degradation, and the saponification value (SV), which measures the total fatty acid content — both free and esterified as triglycerides. The acid value is determined by direct titration of the dissolved oil against 0.1 N alcoholic KOH after dissolving the oil in a neutral 1:1 diethyl ether:ethanol solvent. The saponification value requires a back titration: the oil is refluxed for 60 minutes with a measured excess of 0.5 N alcoholic KOH, and the unreacted KOH is back-titrated with standardised 0.5 N HCl. The ester value (EV = SV − AV) represents the KOH required to saponify only the triglycerides. Reference values are provided for groundnut oil (SV 185–195), coconut oil (SV 250–264), and fresh lubricating oil (AV < 0.5). A high AV in lubricating oil signals oxidative degradation and corrosive acid formation. Diethyl ether (flash point −45°C) requires mandatory fume hood use and no open flames.