There are two versions of Naphthol available for commercial use: 1-Naphthol and 2-Naphthol. Both types are soluble in chloroform, ethers, and simple alcohols. Both 1-Naphthol and 2-Naphthol are used in humans and livestock as a biomarker to see if the subject has been exposed to polycyclic aromatic hydrocarbons. 1-Naphthol is a white fluorescent solid. The structural difference between 1-Naphthol and 2-Naphthol is the location of the hydroxyl group on the naphthalene ring. 1-Naphthol is used as a precursor for some insecticides, pharmaceuticals, and azo dyes. It can be used for running various tests, such as Molisch’s test, rapid furfural test, Voges-Proskauer test, or Sakaguchi test. 2-Naphthol is a colorless or sometimes yellow crystalline fluorescent solid. 2-Naphthol is used for creating dyes. It makes Sudan dyes one through four. It’s also the precursor to BINOL, a substance also used for creating dyes and organic synthesis.