Experimental excess volumes VEfor 23 binary liquid mixtures consisting of polar (ethers, alcohols, amines or chloride hydrocarbons) + non polar components are compared with theoretical predictions of the equations of state of Snider and Herrington, and Guggenheim. The former predicts satisfactorily the sign of experimental VEvalues in most of the cases, while the latter gives systematically large negative values. The one-fluid and two-fluid relations do not differ generally in their results.