An acidic solution of sparingly-soluble Group IIA complexes (“AGIIS”), its preparation and its uses. 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 various uses include cleaning, food production, decontamination, bioremediation, agricultural application, medical application, and detoxification of substances.