  We have used specific heat and neutron diffraction measurements on single
crystals of URu$_{2-x}$Fe$_x$Si$_2$ for Fe concentrations $x$ $\leq$ 0.7 to
establish that chemical substitution of Ru with Fe acts as "chemical pressure"
$P_{ch}$ as previously proposed by Kanchanavatee et al. [Phys. Rev. B {\bf 84},
245122 (2011)] based on bulk measurements on polycrystalline samples. Notably,
neutron diffraction reveals a sharp increase of the uranium magnetic moment at
$x=0.1$, reminiscent of the behavior at the "hidden order" (HO) to large moment
antiferromagnetic (LMAFM) phase transition observed at a pressure $P_x\approx$
0.5-0.7~GPa in URu$_2$Si$_2$. Using the unit cell volume determined from our
measurements and an isothermal compressibility $\kappa_{T} = 5.2 \times
10^{-3}$ GPa$^{-1}$ for URu$_2$Si$_2$, we determine the chemical pressure
$P_{ch}$ in URu$_{2-x}$Fe$_x$Si$_2$ as a function of $x$. The resulting
temperature $T$-chemical pressure $P_{ch}$ phase diagram for
URu$_{2-x}$Fe$_x$Si$_2$ is in agreement with the established temperature
$T$-external pressure $P$ phase diagram of URu$_2$Si$_2$.
