Structure and properties of commercial Chitosan-50 powder ((C6H11NO4)n, M=500.000, Wako Pure Chemical Industries Ltd.) were investigated. XRD, IR spectroscopy, DTGA and SEM were used. It was shown that chitosan powder is characterized only by chitosan phase and flaky flat irregular particles and agglomerates sized from 5 nm to 200 μm. Decomposition of chitosan is complete at 580 °C. Specific surface area, which was measured by nitrogen adsorption-BET method, is equal to 0.80±0.01 m2/g and skeleton density, which was measured by helium pycnometery, is equal to 1.49±0.01 g/cm3. According to zeta potential investigation it was established that chitosan is characterized by electrostatic stability in ethanol and isopropanol and lack of electrostatic stability in water and acetone.