C4H4O

from The Collaborative International Dictionary of English v.0.48

Furfuran \Fur"fu*ran\, n. [L. furfur bran.] (Chem.)
   A colorless, oily substance, {C4H4O}, obtained by distilling
   certain organic substances, as pine wood, salts of pyromucic
   acid, etc.; -- called also {tetraphenol}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Glycolide \Gly"co*lide\, n. [Glycol + anhydride.] (Chem.)
   A white amorphous powder, {C4H4O}, obtained by heating and
   dehydrating glycolic acid. [Written also {glycollide}.]
   [1913 Webster]

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