The compression curve (void ratio, $e$ vs. effective stress, $\sigma_{\mathrm{v}}^{\prime}$ ) for a certain clayey soil is a straight line in a semi-logarithmic plot and it passes through the points $\left(e=1.2 ; \sigma_{\mathrm{v}}^{\prime}=50\right.$ $\mathrm{kPa}$ ) and $\left(e=0.6 ; \sigma_{\mathrm{v}}^{\prime}=800 \mathrm{kPa}\right)$. The compression index (up to two decimal places) of the soil is
The compression curve (void ratio, $e$ vs. effective stress, $\sigma_{\mathrm{v}}^{\prime}$ ) for a certain clayey soil is a straight line in a semi-logarithmic plot and it passes through the points $\left(e=1.2 ; \sigma_{\mathrm{v}}^{\prime}=50\right.$ $\mathrm{kPa}$ ) and $\left(e=0.6 ; \sigma_{\mathrm{v}}^{\prime}=800 \mathrm{kPa}\right)$. The compression index (up to two decimal places) of the soil is