  We use experimental and simulation data from the literature to infer five
characteristic lengths, denoted $\xi_s$, $\xi_f$, $\xi_\Pi$, $\xi_\phi$, and
$\xi_D$ of a semidilute polymer solution. The first two of these are defined in
terms of scattering from the solution, the third is defined in terms of osmotic
pressure, the fourth by the spatial monomer concentration profile, and the last
by co-operative diffusion. In a given solution the ratios of any of these five
lengths are expected to be universal constants. Knowing these constants thus
allows one to use one measured property of a solution as a means of inferring
others. We calculate these ratios and estimate their uncertainties for
solutions in theta as well as good-solvent conditions. The analysis is
strengthened by use of scattering properties of isolated polymers inferred from
computer simulations.
