Hydrochloric acid is chemically written as HCl and is a strong acid known to have no color or smell. It is in fact a term to require a solution of hydrogen chloride and water. Hydrogen chloride is an acid that is an outcome of a response in between chlorine and hydrogen gas which results to an explosive development of the acidic gas. Ordinarily it is called muriatic acid, discovered in homes as a cleaning agent, yet extremely corrosive. http://www.thegreenbook.com/products/hydrochloric-acid/
remove rust stains. All-purpose cleaners won't remove rust stains from sinks, tubs and toilets, even with a lot of elbow grease. The trick is to use a stain remover like Super Iron Out ($10 for a 5-lb. jug). Look for a rust stain remover or a product that contains diluted hydrochloric acid (also listed on product labels as hydrogen chloride, HCL or muriatic acid). Be careful not to use a product containing bleach—it'll set the stain.