To: E. Charters who wrote (82773 ) 3/4/2002 8:50:19 AM From: Richnorth Read Replies (1) | Respond to of 116796 << The three salts make aqua regia. The additional acid is sulfuric, which is made by the (FeAl)2(So4)3 and the FeS2 being dissolved. The sulfate or iron and aluminum dissolves quickly. >> Your formula of (FeAl)2(SO4)3 cannot be correct as it would suggest the charge on the Fe to be 0. Maybe the salt you were talking about was a complex salt consisting of the sulfates of Fe and Al as in the natural salt hydrate, Fe2(SO4)3.Al2(SO4)3.18H20. In this case, the charge on the Fe ion is 3+. Now both this ion and the Al3+ ion hydrolyze in water to give H+ ions making the water acidic. Even so, I am still skeptical. Why it worked for the Incas and the Quechas, I don't know. Maybe I am missing something????? ======================================== ---pedantic --- aqua regia Pronounced As: äkw rj [Lat.,=royal water], corrosive, fuming yellow liquid prepared by mixing one volume of concentrated nitric acid with three to four volumes of concentrated hydrochloric acid. It was so named by the alchemists because it dissolves gold and platinum, the "royal metals, which do not dissolve in nitric or hydrochloric acid alone. Its fumes and yellow color are caused by reaction of nitric acid, HNO3, with hydrogen chloride, HCl, to form nitrosyl chloride, NOCl, chlorine, Cl2, and water; both chlorine and nitrosyl chloride are yellow-colored and volatile. The nitrosyl chloride further decomposes to nitric oxide, NO, and chlorine. Nitric acid is a powerful oxidizing agent (see oxidation and reduction), but the chemical equilibrium for its reaction with gold, Au, only permits formation of a tiny amount of Au+3 ion, so the amount of gold dissolved in pure nitric acid is undetectable. The presence of chloride ion, Cl-, allows formation of the stable chloraurate complex ion, AuCl4-. Because of the high concentration of chloride ion in aqua regia, the Au+3 is reacted almost as soon as it is formed, keeping its concentration low; this allows oxidation of more Au to Au+3, and the gold is dissolved. The gold may also react directly with the free chlorine in aqua regia, since chlorine is a powerful oxidizing agent. Aqua regia can dissolve gold because each of its two component acids carries out a different function. The nitric acid is a good oxidizing agent. Chloride ions from the hydrochloric acid from coordination complexes with the gold ions, removing them from solution. Reducing the concentration of the Au3+ ions shifts the equilibrium towards the oxidized form. Reaction equation: Au(s ) + 3NO3-(aq ) + 6H+(aq ) ----> Au3+(aq ) + 3NO2(g ) + 3H2O(l ) Au3+(aq ) + 4Cl-(aq ) -----> AuCl4-(aq ) ---pedantic ---