(also rhodanide), any of the salts of thio-cyanic acid, HSCN. Although most thiocyanates are freely soluble in water, AgSCN, CuSCN, and Hg(SCN)2 are insoluble. Colorless KSCN and NH4SCN are widely used in analytical chemistry for cation detection; for example, with Fe3+ they form bloodred Fe(SCN)3, and with Cu2+ in an ammonium medium they form blue [Cu(NH3)4](SCN)2.