A bath for removing gold from plated articles without dissolving the
base in order to save the precious metal. A bath of 10 parts of
potassium cyanide and 100 parts of water may be used, the articles to be
stripped being immersed therein as the anode of an active circuit. If
the gilding is on a silver or copper basis, or on an alloy of these
metals the same solution attacks the base and dissolves it, which is
objectionable. For silver articles it is enough to heat to cherry red
and throw into dilute sulphuric acid. The gold scales off in metallic
spangles. For copper articles, a mixture of 10 volumes concentrated
sulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acid
may be used by immersion only, or with a battery. The sulphuric acid in
such large excess is supposed to protect the copper. For copper articles
concentrated sulphuric acid alone with the battery may be used. This
does not sensibly attack the copper if it is not allowed to become
diluted. Even the dampness of the air may act to dilute it.