Thermomechanical properties of poly(acrylic acid-co-acrylamide) hydrogels have been measured for a range of gels while systematically varying the acrylamide/acrylic acid ratio. The gels have been equilibrated with a buffer solution at constant pH and salinity. The gels were characterized in terms of their equilibrium swelling ratio, elastic modulus, and electrochemical potential. The results are in quantitative agreement with the predictions from a recently published thermodynamic field theory.