Brief communication A quantitative analysis on latent heat of an aqueous binary mixture q

AbstractThe latent heat during phase change of water–NaCl binary mixture was measured using a differential scanning calori-meter, and the magnitude for two distinct phase change events, water/ice and eutectic phase change, were analyzed con-sidering the phase change characteristics of a binary mixture. During the analysis, the latent heat associated with eachevent was calculated by normalizing the amount of each endothermic peak with only the amount of sample participatingin each event estimated from the lever rule for the phase diagram. The resulting latent heat of each phase change measuredis 303.7 ± 2.5 J/g for water/ice phase change, and 233.0 ± 1.6 J/g for eutectic phase change, respectively regardless of theinitial concentration of mixture. Although the latent heats of water/ice phase change in water–NaCl mixtures are closelycorrelated, further study is warranted to investigate the reason for smaller latent heat of water/ice phase change than thatin pure water (335 J/g). The analysis using the lever rule was extended to estimate the latent heat of dihydrate as 115 J/gwith the measured eutectic and water/ice latent heat values. This new analysis based on the lever rule will be useful to esti-mate the latent heat of water–NaCl mixtures at various concentrations, and may become a framework for more generalanalysis of latent heat of various biological solutions. 2005 Elsevier Inc. All rights reserved.