Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn_2V_2O_7, (Cu_0.56Zn_1.44)V_2O_7, and (Cu_1.0Zn_1.0)V_2O_7. It is found that dependences C _ p = f ( T ) have extremes. The thermodynamic properties of Zn_2V_2O_7 have been determined.