A large-scale non-electrochemical redox synthesis of microcrystalline α-(ET) 2I 3 has been developed. On heating at 100 °C for 5 h, the compound transforms into the polymorphic superconducting phases β co-(ET) 2I 3 (T c ≈ 7.5 K; 92 weight %) and κ-(ET) 2I 3 (T c ≈ 3.6 K; 8 weight %), as evidenced by high resolution X-ray powder diffraction and subsequent Rietveld refinement as well as by AC-susceptibility and DC-magnetization measurements.