The crystal structure of potassium peroxodisulfate was determined. The crystals are triclinic, a =5.115(1),b =7.034(2), c =5.505(1) å, α =106.32(2),gb =90.18(2), γ =106.12(2)‡, Vcell = 181.90(7) å3, space group PĪ, Z =1, dcalc =2.468 g/cm3 [“Syntex P21,” λCuKα, 994 reflections measured in a whole sphere to 2Τmax =114‡, including 496 independent reflections (Rint = 0.0571), R(F) = 0.0391, wR(F2) = 0.0933 for 486 Fhkl > 4Σ(F)]. An absorption correction (Μ = 171.37 cm−1) was applied taking into account the shape and size of the crystal using data about face indices. The representative of the single crystal was proven by comparing the experimental and calculated diffractograms. The geometrical characteristics of S2O82: S-O 1.645(2), S = 0 1.421(3)-1.429(2), O-O 1.495(5) å, S-O-O 106.2(2)‡.