February 22, 2024

Assay of Phenobarbitone: Medicinal Chemistry Practical

Assay of Phenobarbitone: Medicinal Chemistry Practical

BP406P Medicinal Chemistry I Practical


To perform the Assay of Phenobarbitone.


  1. A textbook of Medicinal Chemistry-I, Pragi Arora, Varun Arora, Davinder Kumar, Page no:282,283.
  2. Indian Pharmacopoeia Volume III  2018,Page No:2899,2900.


Sodium hydroxide, aldehyde free ethanol, benzoic acid, thymolphthalein solution,

silver nitrate, pyridine and ether, conical flask, burette, beaker, pipette etc.


Phenobarbitone is assayed by non-aqueous titration. In this method, the drug is dissolved in the pyridine and titrated with sodium hydroxide solution using thymolphthalein as an indicator.



Actually weighed  0.6g of benzoic acid and dissolved it in a mixture of 30ml of ethanol and 6ml of water and titrated with ethanolic sodium hydroxide solution using 0.2ml of thymolphthalein as an indicator.


Weighed and powdered  20 tablets. Weighed a quantity of the powder containing about 0.1g (100 mg ) of phenobarbitone in 5ml of pyridine add 0.25 ml of thymolphthalein solution and 10 ml of silver nitrate pyridine reagent and titrated with 0.1M ethanolic sodium hydroxide until the purely blue colour is obtained. Repeated the operation without the substance under examination.

The difference between the titrations represents the amount of sodium hydroxide required.

Equivalent factor: 1ml of 0.1M ethanolic sodium hydroxide=0.01161g of C12H12N2O3


The percentage purity of Phenobarbitone was found to be =

Second Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise

S Y B Pharm Sem IIIS Y B Pharm Sem IV
BP301T Pharmaceutical Organic Chemistry II TheoryBP401T Pharmaceutical Organic Chemistry III Theory
BP302T Physical Pharmaceutics I TheoryBP402T Medicinal Chemistry I Theory
BP303T Pharmaceutical Microbiology TheoBP403T Physical Pharmaceutics II Theory
BP304T Pharmaceutical Engineering TheoryBP404T Pharmacology I Theory
BP305P Pharmaceutical Organic Chemistry II PracticalBP405T Pharmacognosy I Theory
BP306P Physical Pharmaceutics I PracticalBP406P Medicinal Chemistry I Practical
BP307P Pharmaceutical Microbiology PracticalBP407P Physical Pharmaceutics II Practical
BP308P Pharmaceutical Engineering PracticalBP408P Pharmacology I Practical
BP409P Pharmacognosy I Practical

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