Aqueous compositions contain hydrochloric acid at a concentration between 8 wt % and 28 wt % inclusive. The amino acid; hydrochloric acid mole ratio may be between 0.2 and 1.5. Sufficient water is present to dissolve the hydrochloric acid and the amino acid. Such compositions have utility as retarders for acid compositions employed in the stimulation of subterranean formations. Slowing the reaction between the acid and formation helps maximize formation permeability and productivity.