I am attempting to corroborate the efficacy of my computational method of determining molecular isotropic polarizability by comparing with known experimental values. It is my understanding that the best way to do this is to convert the experimental refractive index to polarizability via the Lorentz-Lorenz equation as such: p = (3/(4*pi*N))*((n^2-1)/(n^2+2)). However, I am unsure as to how to obtain N for such an equation. I have seen "N is the number of molecules per unit volume," but I am unsure how to find this. I collected refractive indices from PubChem (e.g. https://pubchem.ncbi.nlm.nih.gov/compound/10659#section=Density). Should I simply use the density of the solid and its molecular weight? This seems problematic as the density has a wide range of values, as does the refractive index.