|pər.]ˌī|ädik-, |per] noun
Etymology: International Scientific Vocabulary per- + iodic
: any of a series of strongly oxidizing acids that are the highest oxygen acids of iodine and may be regarded as derived from a hypothetical iodine heptoxide I 2 O 7 by union with varying amounts of water: as
a. : a hygroscopic crystalline acid H 5 IO 6 obtainable by electrolytic oxidation of iodic acid — called also orthoperiodic acid, paraperiodic acid
b. : an unstable acid HIO 4 that forms stable salts and is obtained as a white residue by dehydration of orthoperiodic acid by heat — called also metaperiodic acid