A plot of $\log \frac{x}{m}$ versus $\log p$ for the adsorption of a gas on a solid gives a straight line with slope equal to :

According to the Freundlich adsorption isotherm, $\frac{x}{m}=k\cdot p^{1/n}$. Taking the logarithm on both sides yields $\log \frac{x}{m}=\log k+\frac{1}{n}\log p$. Comparing this with the equation of a straight line $y=mx+c$, the slope $m$ is $\frac{1}{n}$.