A modified Zeeman scanning method was used to excite selectively the magnetic substates of the $4^{2}P_{\frac{1}{2}}$ potassium atoms mixed with inert gases and placed in a strong magnetic field. The resulting potassium-inert-gas atomic collisions induced ${m}_{J}$ mixing in potassium, which manifested itself by the depolarization of the potassium resonance fluorescence. The polarization measurements yielded the following disorientation cross sections: K-He: 46 ${\mathrm{\AA{}}}^{2}$; K-Ne: 39 ${\mathrm{\AA{}}}^{2}$; K-A: 52 ${\mathrm{\AA{}}}^{2}$; K-Kr: 80 ${\mathrm{\AA{}}}^{2}$; K-Xe: 107 ${\mathrm{\AA{}}}^{2}$.