Does the subject want to ask "what is the reaction between indoquinone and fermented soybean?" It is purplish red. Indoquinone mixed with fermented soybean will show purple color. Light fermented soybean is a fermented product of black mature seeds of leguminous soybean. It is processed everywhere. Bitter, pungent and cool. Enter the lung and stomach meridians. Efficacy: relieving exterior syndrome, relieving restlessness, invigorating stomach, promoting digestion, and stopping sweating. Indoquinone, also called indigo red, is used to make vat dyes and drugs. Used as a reagent for the determination of ketene and thiophene. Take fermented soybean 1g, grind it, add water 10ml, heat it to boiling, keep it slightly boiling for several minutes, and filter it. Take 0.5ml of the filtrate, dot it on the filter paper, dry it, spray it with the mixed solution of1%indoloquinone-acetic acid (10: 1), and dry it at 100 ~10.