A factor that corrects for the compressibility of the carrier gas. The values of the measured quantities obtained after multiplication by the factor $j$ are independent of the pressure drop in the column. If $p_{\text{i}}$, $p_{\text{o}}$ are respectively the pressures of the carrier gas at the inlet and outlet of the column, then $j$ is given by: $$j=\frac{3[(\frac{p_{\text{i}}}{p_{\text{o}}}{)}^2-1]}{2[(\frac{p_{\text{i}}}{p_{\text{o}}}{)}^3-1]}$$