A flow apparatus was established to measure the critical properties of pure components and mixtures. The critical points are visually determined by observing the critical opalescence. The measurement can be carried out up to 10 MPa for pressure and 773 K for temperature. Critical temperatures (T-c) and critical pressures (p(c)) of pure compounds (hexane, heptane, octane, nonane, and decane) and their binary mixtures were measured. Experimental data for hexane + heptane, hexane + octane, hexane + decane, heptane + octane, and heptane +decane are available in the open literature and compare well with our data. On the other hand, the critical properties of hexane + nonane, heptane + nonane, octane + nonane, octane + decane, and nonane + decane systems were presented for the first time in this paper. All the experimental data are correlated by the Redlich-Kister equation.