What is "polythionic acid"

n. (context chemistry English) Any acid of the form H₂S_nO₆ having a chain of sulfur atoms

Polythionic acid is an oxoacid which has a straight chain of sulfur atoms and has the chemical formula HSO (n > 2). Trithionic acid (HSO), tetrathionic acid (HSO) are simple examples. The compounds of n < 80 are expected to exist, and those of n < 20 have already been synthesized. Dithionic acid (HSO) does not belong to polythionic acid due to the difference in the property.