methionic

from The Century Dictionary.

• Noting an acid, a colorless crystalline deliquescent, very stable compound, CH₂(SO₃H)₂, prepared by the action of fuming sulphuric acid on lactic acid, and formed, in small quantity, by the action of sulphuric acid on ether.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Chem.) Of, pertaining to, or designating, a sulphonic (thionic) acid derivative of methane, obtained as a stable white crystalline substance, CH2.(SO3H)2, which forms well defined salts.