hexabasic

Century Dictionary and Cyclopedia

1. Having a basicity of six; capable of combining with a proportion of base or metal equivalent to six atoms of hydrogen.

Wiktionary

1. adj. chemistry, of an acid containing six replaceable hydrogen atoms
2. adj. chemistry having six atoms of a univalent metal

GNU Webster's 1913

1. adj. (Chem.) Having six hydrogen atoms or six radicals capable of being replaced or saturated by bases; -- said of acids.