The Collaborative International Dictionary of English v.0.48:
Manganate \Man"ga*nate\, n. [Cf. F. manganate.] (Chem.) A salt of manganic acid. [1913 Webster] Note: The manganates are usually green, and are well-known compounds, though derived from a hypothetical acid. [1913 Webster]WordNet (r) 3.0 (2006):
manganate n 1: a salt of manganic acid containing manganese as its anion