The master alchemist's voice rang clearly from the stone walls. Anyone hearing it knew immediately that he was Important."The vials are identical," he explained, as if lecturing particularly favored students. "Each contains two oils, yellow and blue, separated by a wax shield. You, sir: Choose one and throw it at the target."The potential customer did so, and the glass tube flew through the air to smash harmlessly against the wall. The master spoke on: "As you can see, nothing happened. Already the volatile blue oil has evaporated. The yellow remains completely inert." At his gesture, an assis