Aim: To perform the assay of Phenoberbetone
Apparatus:
- Erlenmeyer flask
- Volumetric flask
- Pipette
- Burette
Chemical Required:
- Sodium hydroxide
- Aldehyde free ethanol
- Benzoic acid
- Thymolphthalein solution
- Silver nitrate
- Pyridne
- Ether
Principle: Phenobarbetone is assayed by non-aqueous titration. In this method, drug is dissolved in the pyridine and titrated with sodium hydroxide solution using thymolphthalin as an indicator.
Procedure:
a)Standardisation of Sodium Hydroxide Solution:
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 indiactor.
b) Assay of Phenobarbitone:
Weighed and powered 20tablets. Weighed a quality of the powder containg about 0.1g (100mg) of phenobarbitone in 5ml of pyridine add 0.25ml of thymolphthalein solution and 10ml of silver nitrate pyridine reagent and titrated with 0.1M ethanolic sodium hydroxide until a pure blue color 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
Calculation:
Standardization of 0.1M Sodium hydroxide solution
Molarity of NaOH=___________
Where,
W=Weight of benzoic acid
V= Volume of NaOH solution consumed.
a)Determination of Phenoberbitone = 
Where,
Molarity= Molarity obtained from step
V= Volume of sodium hydroxide used
0.01161 is the equivalent factor
Molarity =0.1M
W=weight of sample
Report: The percentage purity of Phenobarbitone wa found to be =_____%
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