Colorimetric method for the determination of the Activity-Concentration of some penicillins

The proposed procedure depends upon hydrolysing penicillin with alkali, thus liberating an equivalent amount of penicilloic acid, which is then allowed to react with an excess of standard ferricyanide. The residual reagent is then determined iodometrically and the consumed ferricyanide would correspond to the total degraded penicillin; that is, originally present and that produced from the intact molecule. Simultaneously, a blank is done with the same amount of penicillin, but without preliminary alkaline hydrolysis. By subtraction, it is only the intact, biologically-active penicillin that is calculated