The design of latent heat thermal energy storage systems is critically dependent on the properties of the chosen Phase Change Material (PCM). Currently published data on the thermodynamic properties of eutectic salts contains contradictory data, impeding the selection of PCMs. In this work, previously elaborated theoretical methods for predicting the composition and enthalpy of fusion for eutectic salt mixtures is experimentally validated for three ternary eutectic mixtures: LiNO3 + NaNO3 + KNO3, Li2CO3 + Na3CO3 + K2CO3, and NaCl + Na2CO3 + Na2SO4. For each combination of salts, the eutectic composition suggested by published sources and the composition predicted by the theory are created. The latent heat of fusion, melting temperature, and congruency of the melting peak of these six mixtures are examined via differential scanning calorimetry. In addition, scanning electron microscopy and energy dispersive spectroscopy are used to verify the expected eutectic structure. Analysis of these six mixtures confirms that the composition can be predicted to within 8%. The enthalpy of fusion can be predicted to within 10% of experimental results. In addition, three binary eutectics (NaCl + Na2SO4, KCl + K2CO3, and NaCl + Na2CO3) are created and the theoretical enthalpy of fusion is experimentally verified.