Ge Hong lived in the 3rd-4th centuries.    He learned alchemy when he was young and knew well about how to preserve health.     He was an expert both in natural and social sciences, especially in chemistry and medicine.  He was one of the most famous practitioner in the Jin Dynasty (265-420) and a learned philosopher.   When cinnabar is heated, suphur inside may combine with oxygen and become sulfur dioxide.  Mercury is thus released.  Mix mercury with sulfur grundum and cinnabar is made.  When cinnabar is heated in an airtight container, its black color will change into red.   He is the author of Bao Pu Zi,  Treatise on Alchemy and Magical Practice.This red mercuric sulfide is one of the first chemosynthesis products of human beings in history.  This is one major contribution of alchemy made to the development of chemistry.