The geometric volume of the part of the tube that contains the packing: \[V_{\text{c}} = A_{\text{c}}\ L\] where \(A_{\text{c}}\) is the internal cross-sectional area of the tube and \(L\) the length of the packed part of the column. In the case of wall-coated open-tubular columns the column volume corresponds to the geometric volume of the whole tube having a liquid or a solid stationary phase on its wall.