# Why would the specific heat capacity of water be used as the specific heat capacity of zinc sulfate?

I could not find the specific heat capacity of zinc sulfate and saw that people use water's heat capacity instead. Why is that?

That said, the NIST database reports a $c_{p}$ for zinc sulfate of 99.01 Jmol$^{-1}$K$^{-1}$ at 298 K.
Looking at the original paper, I found this plot of $c_p$ as a function of temperature. At room temperature, you can see it is roughly 100 Jmol$^{-1}$K$^{-1}$.