Determination of Acetic Acid in Vinegar Principle Acetic acid, can readily be determined by titration with standard base using phenolphthalein indicator. CH3COOH + NaOH ⎯⎯→ CH3COONa + H2O The color change of phenolphthalein (ph.ph.) indicator from colorless in acid medium to faint pink in alkaline medium.

Procedure 1. Pipette 10 ml of vinegar solution into 250 conical flask Procedure 1. Pipette 10 ml of vinegar solution into 250 conical flask. 2. Add 20 ml water, and 2 drops of ph.ph. indicator. 3. Titrate with standard 0.1 N NaOH till the first permanent pink color.

Calculation C% = VS × F × E × 100 Vt or (wt) C% = percentage content of the substance to be determined (either w/v or w/w). VS = volume of the standard solution consumed by the substance to be determined. F = standard factor of the standard solution. E = Milli-equivalent of the substance to be determined i.e. the weight of the substance, which reacts with 1.0 ml of standard solution (calculated from the actual reactions).

Vt = volume taken for titration from the solution of substance to be determined. Wt = weight of the substance to be determined taken for titration. E for Acetic acid 1 ml of 0.1 N NaOH = 0.0060 g acetic acid.

CH3COOH + NaOH ⎯⎯→ CH3COONa + H2O NaOH ≡ CH3COOH 1 mole NaOH = one mole acetic acid M. wt. of acetic acid = 60 40 g = 60 g 1 L 1 N NaOH = 49 g NaOH 1 L 1 N NaOH = 60 g acetic acid 1 ml 0.1 N NaOH = 6 g acetic 1000 1 ml 0.1 NaOH = 0.006 g acetic (E)