  We consider pressure-driven flows of electrolyte solutions in small channels
or capillaries in which tracer particles are used to probe velocity profiles.
Under the assumption that the double layer is thin compared to the channel
dimensions, we show that the flow-induced streaming electric field can create
an apparent slip velocity for the motion of the particles, even if the flow
velocity still satisfies the no-slip boundary condition. In this case, tracking
of particle would lead to the wrong conclusion that the no-slip boundary
condition is violated. We evaluate the apparent slip length, compare with
experiments, and discuss the implications of these results.

Fluid Dynamics;Soft Condensed Matter;General Physics