Spectrophotometric determination of phenothiazine with ferric chloride

An investigation of the fundamental conditions for the photometric quantitative determination of phenothiazine with ferric chloride was made, and it was found to follow the Beer's law in the concentration range of 220 μg/ ml within 2% error by the examination of reproducibility.The reaction products isolated are considered to be phenothiazine-3-one, the oxidized product of phenothiazine, from its physical properties.Various phenothiazine derivatives used as medicinal drugs show the similar coloration with ferric chloride and therefore this method may be applicable to the photometric determination of phenothiazine derivatives.