If the units chosen for N, the total amount present are mol and the units of c are mol mL−1 then the units of VD will be mL. If instead, N is the amount present per unit mass of tissue, stated in mol g−1, then the units of VD are mL g−1. Because the rate constant, k, depends on the volume of distribution, which is determined by the distribution of the substance within the parenchyma, e.g. on binding, sequestration, etc., k is also affected by the distribution of the substance and not just on the processes that govern elimination. As a consequence the rate constant is less suitable than the clearance as a description of elimination.