Density of plutonium oxide I am trying to find the mass density $\rho$ of plutonium dioxide, $\ce{PuO2}$. I could calculate it, but the mass density of oxygen found in the literature is the density of gas oxygen.

So I was wondering where can one find mass densities for compounds that come from experimental measurements?
A quick Google search shows the density to be $11.5~\mathrm{g~cm^{-3}}$.

You might have had trouble finding it since it is actually called plutonium (IV) oxide, as plutonium is an f-block metal (specifically an actinide) displaying multiple  oxidation states (commonly III, IV, V, and VI, while VII is rare).