Page 84 - Analytical Chemistry I E-book

Determination of ester drugs

• Example: determination of aspirin (acetylsalicylic acid).
• Back titration procedure: Measured excess standard NaOH is added,

boil gently for 5-10 min to ensure complete hydrolysis, cool, add
phenolphthalein indicator then titrate the unused excess base using
standard HCl.

NaOH + HCl ⎯→ NaCl + H2O

unreacted
base