|pər, _pə, (ˈ)per+...- - noun
Etymology: per- + New Latin rhen ium + English -ic
: either of two acids formed by the oxidation of rhenium or rhenium compounds of lower valence states and known only in solution or in the form of salts:
a. : the monobasic acid HReO 4 analogous to permanganic acid that forms colorless stable salts — called also metaperrhenic acid
b. : the tribasic acid H 3 ReO 5 that forms yellow salts turning red when heated and hydrolyzed in water to salts of metaperrhenic acid — called also mesoperrhenic acid