Alkahestry (錬丹術, Rentanjutsu), also called Purification Arts (連弾主, Rendan-nushi), refers to the slightly different form of Alchemy used in the country of Xing. Alkahestry differs from Alchemy in both its practice and its goal. Whereas Amestrian Alchemy claims to have its roots in the energy of tectonic shifts and practices manipulation of matter toward scientifically practical ends, Alkahestry is centered on a concept called the "Dragon's Pulse" which speaks of the Earth itself having a constant flow of chi (life energy) which flows metaphorically from the tops of mountains down to the land, nourishing everything it passes with that energy as does blood coursing through the veins. Using this concept, Alkahestrists are capable of a higher level of medical transmutation than Amestrian alchemists - transmitting chi through the pathways of the human body to cure mild ailments as well as minor injuries - and can even project their transmutations over long distances and wide areas by accessing and guiding that current to their own means with Purification Circles and Alkahestric markers, a function of which Amestrian Alchemy is altogether incapable.
The idea of "Alkahestry" is built on the practice of fashioning elixirs and, therefore, is mainly used for medicinal purposes; as such, the focus of the craft is the discovery of the Elixir of Life - the key to immortality and eternal vigor - as opposed to Amestrian Alchemy's preoccupation with the Philosopher's Stone's alchemical augmentation properties.
Four hundred years ago, the practices which would give rise to this Xingese alchemy could not be truly called "alchemy" at all, but a series of misguided attempts at mystical healing through the ingestion of various substances. In fact, it is said that three whole generations of the imperial family died from ingesting mercury because they believed that it promoted longevity. It wasn't until a mysterious figure they call "The Philosopher of the West", who had supposedly come from Xerxes, appeared in Xing with his alchemical teachings that Xingese Alkahestry was born - created from a melding of the new teachings and the old metaphysical healing practices.
May Chang is the only character shown in the series to use Alkahestry, though Scar's alchemy uses alkahestry principles. Van Hohenheim helped create Alkahestry, and has knowledge of it, but is never seen using it. Because of their differing origins, Father cannot control Alkahestry as he does Alchemy.