To curve-fit or not to curve-fit: Comments on ``Water structure enhancement in water-rich binary solvent mixtures. Part II. The excess partial molar heat capacity of the water'' by Yizhak Marcus in this journal

Comments are given to show that for calculating the composition derivative of the mother thermodynamic quantity in obtaining the partial molar quantity, the curve-fitting of the mother function followed by arithmetic differentiation of the resulting function is often dangerous. An example is provided. (C) 2012 Elsevier B.V. All rights reserved.