Investigation of the physicochemical behaviour of <i>Acidum citricum</i> homoeopathic dilutions at temperatures from 293.15 K to 318.15 K by using volumetric, acoustic and viscometric methods

Background: The physicochemical properties of homoeopathic medicines have been gaining importance in elucidating the physicochemical behaviour (interactions) and, hence in establishing the presence of medicine at ultra-high dilutions. Objective: The present study is aimed to reconnoiter the existence of drug in ultra-diluted medicines and evidence regarding the physicochemical behaviour and prevailing interactions in the dilutions of Acidum citricum. Materials and Methods: The densities (ρ), ultrasonic speeds (u) and viscosities (η) of pure ethanol control (91% ethanol in water) and 33 dilutions of Acidum citricum of potencies across 1C to 200C at temperatures from 293.15 K to 318.15 K and at atmospheric pressure. Results: The measured data are used to compute the physicochemical parameters, viz., isentropic compressibility (κs), intermolecular free lengths (Lf), acoustic impedance (Z) relative association (RA), relaxation time (τ), ultrasonic absorption (α/f2) pseudo-Grüneisen parameter (Γ), deviations in isentropic compressibility, (Δκs), deviations in intermolecular free length, (ΔLf), deviations in acoustic impedance (ΔZ), deviations in viscosity (Δη) and deviations in pseudo-Grüneisen parameter (ΔΓ). These parameters specified diverse trends at certain potencies of these homoeopathic dilutions. Conclusion: The results are qualitatively interpreted by means of prevailing interactions of these Acidum citricum dilutions. It is observed that the interactions may take place among H+ and citrate ions and the molecular aggregates of water-ethanol, i.e., dissipative structures. The results specified that even in high-dilutions (50C, 110C, 150C and 160C) the molecules of medicine may still exist in these homoeopathic formulations.