Studies on Polychrome Methylene Blue II. Acid Oxidation Methods of Polychroming

Abstract

The action of K2Cr2O7, Ag2O, KMnO4, HgO and NaIO3 in polychroming methylene blue is explored. The last 2 have no action in neutral or acid methylene blue solns. With the other 3 reagents the amt. of poly-chroming, as measured by the shift in the absorption spectrum, is roughly proportional to the amt. of oxidant used. Various lots of methylene blue produce similar products with similar proportions of K2Cr2O7. With similar quantities of this reagent similar products are produced by polychroming at 100[degree], 80[degree], 70[degree] or 60[degree] C. At 100[degree] C the action of K2Cr2O7 or of Ag2O appears to be completed in 15 mins. In K2Cr2O7 polychroming H2SO4 can be substituted for HC1, and subsequent BaCO3 neutralization removes the salts formed and prevents accidental alkali polychroming. K2Cr2O7 polychroming produces products with narrower absorption bands than alkali polychroming.