Of or derived from this acid.
Mid 19th century (in an earlier sense). From Byzantine Greek ἀλλοϕανής appearing otherwise (from ancient Greek ἀλλο- + -ϕανής) + -ic, originally (in allophanic acid) after German Allophansäure.
Of the nature of or containing the clay mineral allophane; especially designating soils dominated by allophane and related minerals, typically occurring on substrates of volcanic ash and weathered volcanic rocks.
Early 20th century. From allophane + -ic.