The removal of hydrochloric acid utilizing magnesium-aluminum oxide (Mg-Al oxide), as prepared by the thermal decomposition of hydrotalcite (HT), was investigated. Cl- in hydrochloric acid can be removed almost 100% by adding 1.75 times the stoichiometric quantity of Mg0.70Al0.20O at 60 degreesC for 1 h. Mg2+ and Al3+ in solution after the reaction were not recognized, because the solution was weakly alkaline.