Chlorination of CS₂ leads to trichloromethanesulfenyl chloride, Cl₃CSCl, in moderate yields. The oxidation of Cl₃CSCl with H₂O₂ gives Cl₃CSO₂Cl, the chloride of trichloromethanesulfonic acid. Cl₃CSO₂Cl is the crucial product for the preparation of trichloromethanesulfonates (“trichlates”) and has been characterized by IR spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction measurements (P-1, a=609.99(5) pm, b=727.45(6) pm, c=782.49(7) pm, α=80.644(3)°, β=85.175(3)°, γ=88.311(3)°. The acid Cl₃CSO₃H can be gained in form of the hydrate (H₅O₂)[Cl₃CSO₃] in two different modifications (I: monoclinic, P2₁/n, Z=8, a=1292.47(7) pm, b=605.89(2) pm, c=2661.1(1) pm, β=98.708(4)°, V=1672.8(1) ų; II: monoclinic, Cc, Z=4, a=699.80(5) pm, b=1054.72(8) pm, c=1139.88(8) pm, β=95.303(3)°, V=837.7(1) ų. Both modifications have been investigated by IR spectroscopy, thermal analyses and theoretical calculations.