Chlorine sulfonic acid (chemical type: HSO3CL) is a colorless or yellowish liquid, which is highly poisonous. Having a pungent odor and fuming in the air, a compound formed by the substitution of a-oh group of sulfuric acid with chlorine. The molecule is tetrahedron configuration, the substituted group is between sulfuric acid and thionyl chloride, there is tear, mainly used in the sulfonation of organic compounds, the preparation of drugs, dyes, pesticides, detergents and so on.