Hydrogen chloride is a colourless gas with a pungent odour; its aqueous solution is known as hydrochloric acid. Hydrogen chloride is produced by burning hydrogen and chlorine together and is also a by-product of the chlorination of organic compounds. HCl is used in the production of PVC, ferric chloride and silicones.
a colorless, pungent, corrosive gas having a suffocating odor. It is heavier than air and fumes strongly in moist air. Hydrogen chloride is very soluble in water and alcohol and less soluble in ether. In semiconductor processing, hydrogen chloride is used in such processes as etching, oxidation, passivation, and epitaxy. It also is used as a plasma and reactive ion etch of silicon and polysilicon, as well as aluminum metallization.
HCl, gaseous matter, produced in fires from the decomposition of PVC, will turn into hydrochloric acid of the same formula HCl when mixed with moisture through a process called hydrolysis.