Gold parting instead of copper. One part pure gold is alloyed with three parts Sterling silver (inquarting). The resulting six karat (6K) gold can then be parted with dilute nitric acid (one part 68-70% nitric acid to one part DISTILLED water). With the karat gold this low (6K), and over medium high heat, the dilute nitric acid will dissolve the Sterling silver (and other base metals in the karat gold) starting on the outside surface of the 6K gold alloy, working its way into the gold alloy, forming a honeycomb structure as it works its way into the metals. Since nitric acid
Malic acid the racemic mixture, and the (S)- enantiomer may be specifically obtained by fermentation of fumaric acid. Self-condensation of malic acid with fuming sulfuric acid gives the pyrone coumalic acid: Malic acid was important in the discovery of the Walden inversion and the Walden cycle, in which (−)-malic acid first is converted into (+)-chlorosuccinic acid by action of phosphorus pentachloride. Wet silver oxide then converts the chlorine compound to (+)-malic acid, which then reacts with PCl to the (−)-chlorosuccinic acid. The cycle is completed when silver oxide takes this compound back to (−)-malic acid. Malic acid Malic acid is an organic