The invention provides a method of producing a solution of hypochlorous acid and water ("the product solution") having a HOCI concentration that is greater than 100 mg/L (w/v). The method includes subjecting a solution of hydrochloric acid and water ("the reaction solution") to electrolysis and obtaining HOCI in an electrolysis reaction. Also, the method includes adding magnesium carbonate (MgCO3) or strontium carbonate (SrCO3) to any one or more of the reaction solution before subjecting the reaction solution to electrolysis, the reaction solution while subjecting the reaction solution to electrolysis, and to the product solution.
