抄録
In the discoloration test of activated carbon, the use of titanous solution for the determination of residual methylene blue was examined, and a simple, industrially applicable discoloration test by the use of titanium sesquisulfate Ti2(SO4)3 was devised. This method differs from the Merck method in that the excess Ti3+ is back titrated and the reaction of the colored solution and titanous solution is maintained at 60° to prevent the oxidation of the titanium ion, by which a low concentration of the methylene blue solution could be determined. A calibration curve of the consumption of ammonium ferric sulfate used for the back titration of titanium and the concentration of the methylene blue solution was prepared and its use facilitated calculation of the discoloration rate of the activated carbon. Titanous solution was prepared from high purity sponge titanium by dissolving it in dilute hydrochloric or sulfuric acid in carbon dioxide stream, easily affording a high concentration of titanium chloride or sesquisulfate. The comparatively stable crystals of the sesquisulfate were obtained in a good yield by bringing the sulfate concentration to approximately 50% by the addition of conc. sulfuric acid to the solution of sesquisulfate obtained.
