Manganese oxides also react with hydrochloric acid but produce Cl2 gas, so this must be done outdoors or in a well-ventilated area. This is how I
clean my manganese-oxide-covered glass, by adding some HCl and then letting it sit in a plastic box with liquid hydroxide drain cleaner at the bottom
outdoors for a couple of days. It removes the stains pretty well, and there is practically no chlorine smell. |