APPLICATION OF THE BJERRUM ASSOCIATION MODEL TO ELECTROLYTE-SOLUTIONS- II - ENTHALPIES OF DILUTION IN WATER AND NONAQUEOUS SOLVENTS

The association theory based on the Bjerrum model, which had been deve loped for the treatment of apparent and partial molar volumes of elect rolyte solutions, is extended to apparent molar relative enthalpies L- 2,L-phi. Experimental enthalpies of dilution for tetrabutylammonium br omide in acetonitrile, propylene carbonate, and gamma-butyrolactone an d for lithium perchlorate and sodium thiocyanate in acetonitrile were obtained and analyzed with this model. Literature data for various ele ctrolytes in water, acetonitrile, and n-propanol were also reanalyzed. Through the Bjerrum equations, enthalpies of dilution can be extrapol ated to infinite dilution and reliable L-2,L-phi obtained for associat ed electrolytes. The model can be used to estimate the association con stant K-A of the electrolyte and these K-A are compared with literatur e values (generally obtained from conductivity). Considering the diffe rence in the concentration ranges investigated in L-2,L-phi and Lambda measurements, K-A extracted from L-2,L-phi, generally fall within an expected range of deviation from the ones obtained by conductivity, pr ovided that nospecific interactions are present in solution.