soluble in hot concentrated hydrochloric acid, and in solutions of caustic alkalis. The alkaline solutions are of a rose-red color and show a cinnabar-red fluorescence. A tetrabromresorufin is used as a dyestuff under the name of Fluorescent Resorcin Blue. Thioresorcinol is obtained by the action of zinc and hydrochloric acid on meta-benzenedisulfonyl chloride. It melts at 27 °C and boils at 243 °C. Resorcinol disulfonic acid, (HO)2C6H2(HSO3)2, is a deliquescent mass obtained by the action of sulfuric acid on resorcin. It is readily soluble in water and ethanol. Resorcinol is also a common scaffold that is found in a class of anticancer agents, some of which (luminespib, ganetespib, KW-2478, and onalespib) were in clinical trials . Part of the resorcinol structure binds to inhibits the N-terminal domain of heat shock protein 90, which is a drug target for anticancer treatments. History, etymology, and nomenclature Austrian chemist Heinrich Hlasiwetz (1825–1875) is remembered for his chemical analysis of resorcinol and for his part in the first preparation of resorcinol, along with Ludwig Barth, which was published in 1864. Benzene-1,3-diol is the name recommended by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry. Resorcinol is so named because of its derivation from ammoniated resin gum, and for its relation to the chemical orcinol. Toxicity Resorcinol has low toxicity, with an (rats, oral) > 300 mg/kg. It is less toxic than phenol. Resorcinol was named a substance of very high concern under European Union REACH in 2022 because of its endocrine disrupting properties. References External links International Chemical Safety Card 1033 NIOSH Pocket Guide to Chemical Hazards IARC Monograph: "Resorcinol" IUPAC Nomenclature of Organic Chemistry (online version of the "Blue Book") IARC Group 3 carcinogens Endocrine disruptors