Volumetric properties of (4-methylphenol + NaOH) at high temperatures Juan A. Kukuljan a , Lucila P. M endez De Leo a,b , Jorge L. Alvarez a,c , Hugo L. Bianchi a,b,1 , Roberto J. Fern andez-Prini a,d, * ,1 a Unidad de Actividad Qu  ımica, Comisi on Nacional de Energ  ıa At omica, Av. Libertador 8250, 1429, Capital Federal, Argentina b Escuela de Ciencia y Tecnolog  ıa, Univ. Nac. General San Mart  ın, Alem 3901, 1651, San Andr es, Argentina c Universidad Tecnol ogica Nacional, Facultad Regional Bs.As, Medrano 951, 1179, Bs.As., Argentina d Instituto de Qu  ımica F  ısica de Materiales, Ambiente y Energ  ıa, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabell on II, 1428, Capital Federal, Argentina Received 8 December 2002; accepted 21 May 2003 Abstract The densities of aqueous solutions of 4-methylphenol and its mixtures with sodium hydrox- ide were measured as a function of concentration at T ¼ 298 K at atmospheric pressure, and between the temperatures 373 K and 463 K at a pressure of 2 MPa. The partial molar volume at infinite dilution of 4-methylphenol (HCRES) and its sodium salt (NaCRES) were deter- mined by the application of the Pitzer ion-interaction treatment to the solutions neglecting high order terms. The reported values of partial molar volume of 4-methylphenol are in good agreement with literature data. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: 4-Methylphenol; Sodium salt of 4-methylphenol; Partial molar volume; Equilibrium associ- ation constant; Densities J. Chem. Thermodynamics 35 (2003) 1541–1552 www.elsevier.com/locate/jct * Corresponding author. Tel.: +54-11-6772-7175; fax: +54-11-6772-7121. E-mail address: rfprini@cnea.gov.ar (R.J. Fern andez-Prini). 1 Members of the Carrera de Investigador Cient  ıfico y T ecnico of CONICET (Argentina). 0021-9614/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0021-9614(03)00131-9