antozone

from The Century Dictionary.

• noun A substance, formerly believed to be a modification of oxygen, whose chief peculiarity is that it combines with ozone and reduces it to ordinary oxygen. It has been proved to be hydrogen dioxid, H₂O₂.

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

• noun (Chem.) A compound formerly supposed to be modification of oxygen, but now known to be hydrogen dioxide; -- so called because apparently antagonistic to ozone, converting it into ordinary oxygen.

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

• noun chemistry, archaic hydrogen peroxide