A universal Ohm's law is derived for the ion bootstrap current relative to the impurity ions. The contribution driven by qir, the neoclassical plus electrostatic part of the ion heat flux, is found to be Jiz = nie (i||−z||) = 1.5 e2qirBθ/miTi(νiz + 2νii) and the frictional heating of the ions is JizEϕ[1−(1/Zeff)], which typically can be 10% to 15% of the total Ohmic heating when nzZ2⩾ni.