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Aqua regia
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<p>Aqua regia is a <a href="/facts/Mixture/tms8rbmn">mixture</a> of <a href="/facts/Nitric_acid/UDbwGp6s">nitric acid</a> and <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a>, optimally in a <a href="/facts/Molar_concentration/P2WL5b9q">molar</a> ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange, or red within seconds from the formation of <a href="/facts/Nitrosyl_chloride/TxTff8WH">nitrosyl chloride</a> and <a href="/facts/Nitrogen_dioxide/FoLvApPI">nitrogen dioxide</a>. It was so named by <a href="/facts/Alchemy/CEx0U1Em">alchemists</a> because it can dissolve <a href="/facts/Noble_metal/Pe9EKIvU">noble metals</a> such as <a href="/facts/Gold/1znknojp">gold</a> and <a href="/facts/Platinum/qJC6lQf7">platinum</a>, though not all metals. </p>