This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
A colorless or yellowish liquid, with the odor of chlorine, volatile, and easily decomposed by light; sp. gr. 1.074. It has the power of dissolving gold, the king of metals - hence its old name, "aqua regia."
In its full strength this acid is irritant and corrosive; in moderate doses it has an alterative tonic action; it stimulates the glandular system, and is apt to cause salivation and also an increased flow of bile. Its actual chemical composition is not thoroughly known, and its difference in action from the other and simpler mineral acids has not yet been verified.
It is useful in many of the diseases mentioned under nitric acid, but seems to possess exceptional power to influence the liver and glandular structures of the alimentary canal.