Five new reagents are suggersted for determining mercury (II): 2-hydroxytiophenol(HTPh), 2,5-dihydroxythiophenol(DHTPh) 2-hydroxy-5-chlorothiophenol (HXTPh), 2-hydroxy-5-bromthiophenol (HBTPh), 2-hydroxy-5-yodthiophenol (HJTPh).  The molar extinction coefficient is equal to (2.4–3.3)∙10⁴ (450 – 480 nm). The optical density is proportional to 0.2–125 μg of  Hg concentration in 5 ml CHCl₃. The formation of a mixed-ligand compound with ratio Hg(II):HTPh:Аm=1:2:2.