Abstract: Poorna chandrodayam (PC) is an elixir of mercury and gold widely used in Siddha Medicine prepared by kupi pudam process. It is a bright scarlet red coloured powder, soluble in Aqua regia. Content of gold, mercury and sulphur were found to be 9.78, 78.11 and 11.95 g, respectively and 280 ppm of free mercury. XRD and XPS studies revealed the presence of HgS, SEM studies revealed difference in size and agglomeration due to repeated cycles of calcinations, EDAX demonstrated HgS as a main component and a small percentage of Hg as oxide form and a small percentage of gold. IR spectra confirmed the pattern of Mercury sulphide and FTIR confirmed that PC is free of organic compounds. DTA revealed decomposition of water molecules and TGA revealed as mercury sulphide. ICP-OES analysis revealed the presence of mercury (141.76 mg g-1), Calcium (11.68 mg g-1) and gold (0.84 mg g-1). TEM revealed nano range of particles of irregular size in the range of 60-70 nm. Presence of HgS in nanoparticles was further confirmed by EDAX attached with TEM. DLS revealed the particle size near nano range and only 10% were below 112.6 nm. AAS studies revealed the presence of Mercury (143.12%), gold (0.92%) and many other metallic compounds. The studies confirms that PC is converted into an amalgamation process and mostly present as Mercury sulphide along with gold and a small portion of mercury oxide.