An adduct that has an acidic solution of sparingly-soluble Group IIA complexes ("AGIIS") and at least one additive. The AGIIS can be prepared by mixing a mineral acid (such as sulfuric acid), and a Group IIA hydroxide (such as calcium hydroxide) or a Group IIA salt of a dibasic acid (such as calcium sulfate), or a mixture of the two Group IIA compounds, followed by removing the solid formed. The additives can be an alcohol, an organic acid or a surface active agent. The composition has various uses, including cleaning, food production, decontamination, bioremediation, agricultural application, medical application, and detoxification of substances.