Aqua regia (
Latin, lit. "royal water" or "king's water") is a
mixture of
nitric acid and
hydrochloric acid, optimally in a
molar ratio of 1:3. Aqua regia is a yellow-orange fuming liquid. Aqua regia was so named because it can dissolve the
noble metals gold and
platinum. However,
titanium,
iridium,
ruthenium,
rhenium,
tantalum,
niobium,
hafnium,
osmium and
rhodium are capable of withstanding its corrosive properties.