I had tried to calculate the constant using K=p/c, where p is the partial pressure of the solute, and c=bq/(1+bM), where q is the density of the solvent, b is the molality, and M is the molar mass of the solute. I am trying to find where I read it, but I did read somewhere that Henry's Law is only valid for dilute solutions where bM is far less than one, and the q value is close to that of water, neither of which is the case for dissolving Xenon or Argon into fluorocarbon.