xanthic acid: any of a class of unstable organic acids containing sulphur
acid: any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
spermatophyta: seed plants; comprises the Angiospermae (or Magnoliophyta) and Gymnospermae (or Gymnospermophyta); in some classification systems Spermatophyta is coordinate with Pteridophyta (spore producing plants having vascular tissue and roots) and Bryophyta (spore producing plants lacking vascular tissue and roots)