Photoreduction of Methylene Blue by Visible Light in the Aqueous Solution Containing Certain Kinds of Inorganic Salts. I. General Features of the Reaction

Abstract

Abstract It was discovered that the irradiation of the aqueous solution of methylene blue containing various kinds of salts, produces the leuco form of dye; accompanied with this reaction, irreversible photodecomposition of dye and demethylation occurs to some extent. Hydroxide, phosphate and borate were found to be most effective in promoting this photoreduction. Careful studies were performed to counteract the possible effect of impurity. Since the present reaction was considered most certainly to be due to the ultimate fission of water, the analysis for Oxygen and hydrogen peroxide was undertaken. The former was not detected by means of a mass-spectrograph in case of phosphate, but the latter was chemically detected in case of borate buffer. The connection between the quantity of demethylation and that of the formation of leuco dye was investigated and clarified to some extent.