Energy required to grind a given mass of particles from a mean diameter of $12 \mathrm{~mm}$ to $4 \mathrm{~mm}$ is $12 \mathrm{~kJ} \mathrm{~kg}^{-1}$. If energy consumed to grind the same mass of particles of $2 \mathrm{~mm}$ mean diameter to $x \mathrm{~mm}$ mean diameter is $252 \mathrm{~kJ} \mathrm{~kg}^{-1},$ the value of $x$ using Rittinger's Law will be______________
Energy required to grind a given mass of particles from a mean diameter of $12 \mathrm{~mm}$ to $4 \mathrm{~mm}$ is $12 \mathrm{~kJ} \mathrm{~kg}^{-1}$. If energy consumed to grind the same mass of particles of $2 \mathrm{~mm}$ mean diameter to $x \mathrm{~mm}$ mean diameter is $252 \mathrm{~kJ} \mathrm{~kg}^{-1},$ the value of $x$ using Rittinger's Law will be______________