Hydrogen chloride is a colorless, corrosive, a non-flammable gas. It has the characteristic of a penetrating and suffocating odor. Hydrogen chloride will dissolve easily in water. At atmospheric pressure, about 1,000 cubic feet of hydrogen gas dissolves in one cubic foot of water. Hydrogen chloride is less soluble in water when the water temperature increases, and it is also less soluble in alcohol and other organic liquids. The solution, hydrochloric acid, which is a formed from the reaction of hydrogen chloride gas in water, contains 40.3% of hydrogen chloride by mass. Hydrochloric acid reacts with many metals, which form salts or chlorides. Hydrochloric acid is soluble in benzene, alcohol, and ether, but it is insoluble in hydrocarbons, and is reactive with metals, hydroxides, amines, and alkalis. Hydrochloric acids have a very penetrating odor. Nearly all metals except for mercury, silver, gold, platinum, tantalum, and certain alloys, corrode when they are exposed to aqueous solutions of hydrochloric acid.

    In water, the hydrogen chloride molecules ionize. When the molecules ionize, they become positively charged hydrogen ions and negatively charged chloride ions. Hydrochloric acid is a good conductor of energy because hydrogen chloride ionizes easily. When hydrogen chloride ionizes, the positively charged hydrogen ions give hydrochloric acid its acidic properties. Because of the hydrochloric acid having acidic properties, all the solutions of hydrogen chloride and water have a sour taste. All the solutions also corrode active metals which form chlorides and hydrogen, turn litmus red, neutralize alkalis, and react with salts or weak acids, and form chlorides and weak acids.