Isothermal molar volume data of (acetonitrile + water) mixtures, between T = 273.15 K and T = 318.15 K, extracted from different sources are combined and treated as a single set to even out minor differences between sources and to increase the number of data points for each temperature. Tikhonov regularization is applied to compute the isothermal first and second derivatives of these data with respect to molar composition. For the reference temperature of 298.15 K, this computation is extended to the third derivative. Generalized Cross Validation is used to guide the selection of the regularization parameter that keeps noise amplification under control. The resulting first derivatives are used to construct the partial molar volume curves which are then checked against published results. Properties of the partial molar volumes are analysed by examining their derivatives. Finally the general shape of the second derivative curve of molar volume is explained qualitatively in terms of tripartite segmentation of the molar composition interval but quantitative comparisons are required to confirm this explanation. (C) 2007 Elsevier Ltd. All rights reserved.