Density - porosity relation graph

$\phi$ Porosity:
$$\phi = {\rho_g-\rho_b \over \rho_g-\rho_f}$$
$\rho_b$ Density bulk:
$$\rho_b = {\phi\rho_f+(1-\phi)\rho_g}$$
$\rho_g$ Density of grain:
$$\rho_g = {\rho_b-\phi\rho_f \over 1-\phi}$$
$\rho_f$ Density of fluid:
$$\rho_f = {\rho_b - (1-\phi)\rho_g \over \phi }$$
Density mix of grains ($G$ is the volume fraction of a grain component):
$${\rho _g}_{mix} = {G_1\rho_G{_1} + G_2\rho_G{_2}+ G_3\rho_G{_3}+ ... +(1-G_1-G_2-G_3 ...-G_{n-1})\rho_n}$$
Density mix of fluids ($F$ is the volume fraction of a fluid component)
$${\rho _f}_{mix} = {F_1\rho_F{_1} + F_2\rho_F{_2}+ F_3\rho_F{_3}+ ... +(1-F_1-F_2-F_3 ...-F_{n-1})\rho_n}$$