It depends on the recipe you're using,the term "mercury" has a LOT of different meanings. It could be mercury (Hg),it could be Mercury (the god),it could be mercury (the planet), or it could be philosophic Mercury which does not have any Hg in it. These are all distinct from "quick silver" which is actually silver metal dissolved in mercury metal(amalgam).
If you could post the recipe in question I could help you much more easily.