Physicochemical Characterization of Soodha Gandhi Dhara Chenduram by X-Ray Powder Diffraction: Confirmation of Cinnabar as the Predominant Crystalline Phase

Abstract

Soodha Gandhi Dhara Chenduram is a classical Siddha mercurial formulation (Chenduram) prepared using purified mercury (Soodham), Sulphur (Gandhagam), and arsenic trisulphide (Aridhaaram) in a ratio of 3:1: ½ through the traditional Kajjali preparation followed by subsequent incineration. The present study aimed to characterize the crystalline phases formed during the Siddha preparation process using X-ray Powder Diffraction (XRD), thereby providing physicochemical evidence for the transformation of the starting materials. XRD analysis revealed cinnabar (HgS, α-phase) as the predominant crystalline phase, with a score of 80 and a scale factor of 0.791. Dipotassium Sulfate Alpha (K₂SO₄) was identified as a minor crystalline phase, with a score of 22 and a scale factor of 0.121. The diffraction pattern exhibited a dominant peak at 2θ=31.14° with a d-spacing of 2.87 Å and relative intensity of 100%, along with a major peak at 2θ=26.44° with a d-spacing of 3.37 Å and relative intensity of 86.46%. These reflections are consistent with the characteristic diffraction pattern of trigonal Cinnabar. The predominance of HgS demonstrates the conversion of mercury and sulphur into a crystalline mercury sulphide phase during the traditional processing steps. The findings support the occurrence of substantial physicochemical transformation during Kajjali formation and subsequent incineration, resulting in a predominantly crystalline HgS-containing product. The identification of defined crystalline phases provides useful information for physicochemical characterization, quality assessment, and standardization of Soodha Gandhi Dhara Chenduram. The study also contributes to the scientific understanding of the traditional Siddha pharmaceutical process and provides a basis for further investigations into its physicochemical properties and therapeutic relevance.