saturant

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Serving to saturate.
• noun A substance used to saturate.

from The Century Dictionary.

• Saturating; impregnating or soaking to fullness.

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

• adjective Impregnating to the full; saturating.
• noun (Chem.) A substance used to neutralize or saturate the affinity of another substance.
• noun (Med.) An antacid, as magnesia, used to correct acidity of the stomach.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A substance which is used to saturate another.
• noun medicine An antacid, such as magnesia, used to reduce stomach acidity.