What is another word for "diluent"?

Roget's Thesaurus (1911) lists these synonyms for "diluent": add, affuse, affusion, aqua, aquatic, aqueous, are, balneal, balneation, bath, bathe, dabble, deluge, dilute, diluted, dilution, dip, douche, douse, drench, drown, duck, flood, gargle, high, humectation, hydrous, immerge, immerse, immersion, infiltration, inject, inundate, irrigate, irrigation, lave, lotion, lymph, lymphatic, macerate.