Ferric chloride (FeCl₃) is an iron-based salt. When dissolved in water, it results in a brown, foul-smelling, corrosive liquid used to etch copper-based metals and stainless steel and in treating sewage and drinking water.

The most common non-industrial use of ferric chloride is in the etching of printed circuit boards by electronics hobbyists.

The chemical is sometimes used by American coin collectors to identify the dates of Buffalo nickels that are so badly worn that the date is no longer visible.

External link

Inchem Data Sheet and MSDS (http://www.inchem.com.ph/fecl3.htm)