2.1.1. Chemicals and Reagents

All the chemicals used were of analytical grade. Sodium molybdate (Na2MoO4·2H2O), ammonium persulfate ((NH4)2S2O8) and hydrochloric acid were purchased from Thermo Fisher Scientific, New Delhi, India. Thioacetamide (C2H5NS), silicotungstic acid AR [H(Si(W3O10)4)·xH2O] and aniline (C6H5NH2), with 99% purity, were purchased from Sigma Aldrich (Steinem, Germany). A stock solution of divalent mercury ions (Hg(NO3)2) of 1000 mg L−<sup>1</sup> was bought from Agilent (Melbourne, Australia) and used after successive dilutions. A 1 M of HNO<sup>3</sup> and NaOH solution was used to adjust the sample pH.
