The heat capacity of Mn(NO3)2.6 H2O is about 0.5113 Cal/gr at 298.2K and 0.530 Cal/g in the range of 298.2–370.45 K.
Reference:
Ref: Energies and equilibria in the decomposition of nitrates of manganese, magnesium, calcium, barium, and aluminum and reactions of nitrogen peroxide