A Consideration of French's Test of Basic Fuchsin for Endo's Medium

Abstract

In describing a method of testing for the return of color in decolorized fuchsin for use in Endo Medium, French states that variations in hydrogen ion concentration fail to influence the appearance of color in this medium.Duplications of this test were made using alcoholic and aqueous solutions of fuchsin and both sodium sulfite and sodium bisulfite as decolorizing agents.In the decolorized alcoholic solutions of fuchsin the color failed to reappear when formalin was added, but a small amount of a weak solution of lactic acid caused the color to return.Alcoholic solutions of fuchsin failed to decolorize in sodium bisulfite solutions until a few drops of NaOH were added. The color, then, reappeared immediately.Solutions of peptones to which fuchsin had been added were substituted for the original fuchsin solution. Alcoholic and aqueous solutions of fuchsin were added to equal amounts of a 1% peptone solution. The peptone solutions varied in their hydrogen ion concentration and the results showed that those...