Name of hydrochloric acid, hydrochloric acid, hydrogen chloride (chemical formula: HCl) of the water solution is acid. It is a strong acid, concentrated hydrochloric acid is highly volatile, so filled with hydrochloric acid to open the container after see mist at the top, that is hydrogen chloride after evaporation and water vapour in the air with small droplets of hydrochloric acid. Hydrochloric acid is a common chemical. In general, the mass fraction of hydrogen chloride in concentrated hydrochloric acid is about 38%. Hydrochloric acid is mainly used in hydrometallurgy of rare metals, organic synthesis, metal processing, food industry, pharmaceutical manufacturing, chemical analysis and dye industry, etc..