A toxic, white powder that is prepared by heating aniline with sulfuric acid. A 1% solution of aniline sulfate can be used as a reagent for the detection of mechanical pulp paper. Lignin containing fibers, such as groundwood or jute, give a positive yellow color reaction. Cotton, linen, and turn the solution brown. A pink color is a positive reaction for the presence of esparto grass (Roberts and Etherington 1982).