Pit"ta*cal (p&ibreve;t"t&adot;*kăl), n. [Gr. pi`tta, pi`ssa, pitch + kalo`s beautiful: cf. F. pittacale.] (Chem.) A dark blue substance obtained from wood tar. It consists of hydrocarbons which when oxidized form the orange-yellow eupittonic compounds, the salts of which are dark blue.