HgCl2, or mercury(II) chloride, is a chemical compound consisting of mercury and chlorine. It appears as a white crystalline solid and is highly soluble in water. Due to its toxic nature, it is classified as a hazardous substance and can pose serious health risks if ingested or inhaled. This compound has various applications, including use in laboratories as a reagent and in the preparation of other mercury compounds. Historically, HgCl2 was used in medicine as a disinfectant and antiseptic, but its use has declined due to safety concerns related to mercury toxicity.