Emeraldine base (EB) form of polyaniline (PANI) powder is prepared by chemical oxidative polymerization using different acidic media (HCl or CF(3)COOH) at different temperatures (-15 degrees C to +5 degrees C). The chemical structure, thermal characterization and conducting behaviour are studied by means of Fourier transform infra-red (FTIR) spectroscopy, differential scanning calorimetery (DSC) and two-probe conductivity method. These polyanilines are soluble in N-methyl-2-pyrrolidone, dimethyl sulfoxide (DMSO) and dimethylpropylene urea (DMPU). The softening temperatures of different EB range from 87.8-116.4 degrees C, which is believed to be an indication of cross-linking. Conductivity of emeraldine base of PANI is around (0.8-1.5) x 10(-6) S/cm and energy band gap is approximately 0.5 eV, and no detectable crystallinity is observed. Wide-angle XRD technique indicates that PANI- EB base is amorphous in nature.