Standard preparation— Using Penicillin G Potassium RS, prepare as directed for Standard preparation under Iodometric Assay—Antibiotics 425.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer a portion of the powder, accurately weighed, equivalent to about 200,000 Penicillin G Units, to a 100-mL volumetric flask, add 10 mL of 1.0 N sodium hydroxide, and mix. Allow to stand for 15 minutes, add 10 mL of 1.2 N hydrochloric acid, dilute with water to volume, and mix. Pipet 2 mL of this solution into a glass-stoppered, 125-mL conical flask.

Blank preparation— Transfer an accurately weighed portion of the powdered Tablets remaining from the preparation of the Assay preparation, equivalent to about 200,000 Penicillin G Units, to a 100-mL volumetric flask, dilute with Buffer No. 1 to volume, and mix. Pipet 2 mL of this solution into a glass-stoppered, 125-mL conical flask.

Procedure— Proceed as directed for Procedure under Iodometric Assay—Antibiotics 425, except in performing the Inactivation and titration to omit the addition of 1.0 N sodium hydroxide and 1.2 N hydrochloric acid, and in the Blank determination to use the Blank preparation in place of the Assay preparation. Calculate the quantity, in Penicillin G Units, in the portion of Tablets taken by the formula: in which T is the labeled quantity, in Penicillin G Units, in each Tablet, and D is the concentration, in Penicillin G Units per mL, of the Assay preparation on the basis of the labeled quantity in each Tablet and the extent of dilution.