Measurements of the isobaric specific heat capacity of {xH(2)O + (1 -x)NH3} with x = (0.0000, 0.1566, 0.1597, 0.3030, 0.3048, 0.4956, 0.7061, and 0.8489) were carried out by the calorimeter with the thermal relaxation method, which we have developed, at T = (280, 300, 320, and 360) K over the pressure range from (0.1 to 15) MPa. The comparison of the present c, values with the literature data as well as the calculated c(p) values by the equations of state (EoS) is presented. The behaviour of the present c(p) values are correlated as a function of temperature, and mole fraction, at p = 5 MPa. (C) 2007 Elsevier Ltd. All rights reserved.