The des Cloiseaux law II similar to C-9/4 describing the scaling relation between osmotic pressure and concentration in semi-dilute solutions of neutral polymers in athermal solvent(good solvent) was tested on nullulan, which is a linear polysaccharide, using membrane osmometry. The experimentally determined exposure is 2.2865 + 0.026, which agrees well with this power law and disagrees with the theoretical value of 2 based on the mean field approximation.