|Parpati literally means crust. They are called so because of their typical crust like appearance. It is the introduction of the parpati by pioneer of Indian pharmaceutics Acharya Nagarjuna in his treatise Rasendra mangal written in 8th century himself for treatment of obstinate skin disorders that pioneered the use of mercury as a therapeutic agent for internal use. Their introduction revolutionized the management of GIT disorders and harbingered a new era in treatment of Pediatric problems.
They are prepared by cooking kajjali (special black compounds made by triturating Mercury and Sulphur together in a crucible) at temperature of 115-120 oC and then pressing it between two flat leaves like that of banana and let it cool down by itself. By doing so mercury is freed of its undesirable properties and gets impregnated with detoxifying and rejuvenating properties.