alchemical poison detection

"You don't need a good taster if you have a good alchemist, but they cost about the same."   -Duke Nanda Frymar

  alchemy ultimately boils down to being the science of transformation. One common effect from alchemical reactions is color changing. This is usually used to teach apprentice alchemists basic reactions in a safe way or to entertain children, but eventually an alchemist who was also a doctor and herbalist came up with the idea of using alchemical color changing as a diagnostic tool.   Certain alchemical mixtures change colors in the presence of certain poisons. This has been used by many nobles to protect themselves against food or drink based poisons.   Certain alchemical mixtures change colors in the presence of certain diseases but this is uncommonly used because each disease requires a specific concoction whereas one alchemical concoction can detect many kinds of poisons.   Disease detectors are often used to control specific plagues or to test communal water supplies.   Certain substances can react with blood samples to cause color changes in the presence of certain conditions but at this is mostly used for autopsies rather than in a diagnosis/prevention manner.   With advanced training (and expensive ingredients) alchemists can concoct mixtures that cause color changes when exposed to supernatural curses.