[Studies on activated charcoal concerning the determination of sulfate in food coal-tar dyes]

It is very difficult to determine the content of sulfate in food coal-tar dye by the method designated in the "Japanese Standards of Food Additives(V)", because the endpoint on titration is difficult to gauge. We determined the concentration of sulfate in food dye nephelometrically after decolorization with charcoal but obtain different values depending on the kind of charcoal used. Because the adsorbed or eluted sulfate in the various charcoals were dispersed widely, so we tested the sulfate contents in five kinds of charcoals. It was found that all kinds of charcoals eluted or adsorbed sulfate in varying degrees. Therefore no charcoal was found to be satisfactory for use in the sulfate test.