Illustrated Glossary of Organic Chemistry

Hydrochloric acid (muriatic acid): An aqueous solution of HCl, containing up to 35% by weight HCl. Best described as H3O+ Cl-. A strong acid; H3O+ pKa -1.78. When hydrochloric acid is saturated or supersaturated with HCl it is called concentrated hydrochloric acid.

Lewis structure of hydronium chloride.