The Transference number of ions varies with the change of concentration; such changes are quite complicated and the extent of change is also small. Transport number also depends on the temperature; t+ usually increases slightly with rising in temperature. The anion transport number, therefore, generally decreases with the increase of temperature. In Table, the transport numbers of some cations are given.
Table: Cation Transport Number at 20°C
For the same cation or the anion, the transport number depends on the electrolyte. Thus t+ values for K+ in KCl, KBr, and KNO3 are 0.490, 0.488 and 0.508 respectively. Similarly t– values for Cl– in HCl, LiCl, NaCl and KCl are 0.177, 0.662, 0.605 and 0.510 respectively. This is easy to understand because the transport number is not a unique property of the ion but depends on the relative speeds of the cation and anion in an electrolyte.