Hypactic fluid

A chemical mixture used in alchemy to test the provenance of gold and diamonds. It may have something in common with Roundworld's acqua regia, the mix of strong acids known to be one of the few things which chemically react with gold. This was used in Equal Rites to test the veracity of gemstones claimed as spircles. On her first appearance in Feet of Clay, Cheery Littlebottom mentions Aqua Quirmis as an acid-based chemical reagant: this may be an alternate name.