SURFACE-TENSION OF AQUEOUS LITHIUM BROMIDE SOLUTIONS CONTAINING 1-OCTANOL AS A HEAT-TRANSFER ADDITIVE

The surface tension of simulated heat-pump working fluids, aqueous sol utions of lithium bromide containing I-octanol, has been measured, for the first time using a recently developed technique (Ishida et al., R ev. Sci. Instrum. 64, 1324 (1993)) which is inherently suitable for ch aracterizing the surfactant solution surfaces from the aspects of ther modynamic adsorption equilibrium and adsorption kinetics. The measurem ent has revealed that even the highest-grade reagents of lithium bromi de commercially available are not necessarily free from surfactant imp urities. Obtained data on the surface tension vs l-octanol concentrati on have been examined on the basis of an equilibrium adsorption model. Through the optimal fitting of the Langmuir-type surface equation of state to the data, we have calculated the 'surface tension vs surface excess' relation and also the variation in 'surface tension vs 1-octan ol concentration' relation with the surface area per unit volume of a given solution.