The enthalpies of dilution of aqueous solutions of RbCl, CsCl, NaF, NaBr, NaI, CaCl 2, SrCl 2, BaCl 2, NaHCO 3, and Na 2CO 3 in the molality range 0.1 to 1.0 mol kg −1 have been determined at 303.15 K with a microcalorimeter. The relative apparent molar enthalpies L φ of these solutions have been determined with the aid of an extended form of the Debye-Hückel limiting law: L φ = S HI 1 2 [{1 + (I/m θ) 1 2 } −1 − σ/3] + BI + CI 3 2 , where S H is the limiting-law slope, σ = “; 3 ( I m ⊖ ) 3 2 ’;[“;1 + ( I m ⊖ ) 1 2 ’; − “;1 + ( I m ⊖ ) 1 2 ’; −1 − 2 ln“;1 + ( I m ⊖ ) 1 2 ’;] , B and C are empirical constants, I is ionic strength, and m ⊖ is a standard molality (1 mol kg −1). This equation fits the experimental results with a standard deviation of ±2 cal th mol −1 for all the salts. The parameters B and C were examined by relating them to properties of the ions that make up the various electrolytes; B was found to be linearly related to the reciprocal of the crystallographic radius and C was found to be directly related to B.