A compound that ionizes in water to produce hydrogen ions. It readily donates protons to other substances and, when dissolved in water, creates solutions that conduct electricity (as in car batteries), taste sour (lemon juice!) and turns litmus paper red. Inorganic acids (sometimes called mineral acids) include sulphuric, nitric, hydrochloric and phosphoric and these are commonly used in toilet cleaners and descalers. Organic acids include acetic (found in vinegar), oxalic, and citric. Rust removers also contain various proportions of the above acids.