Abstract 
I will discuss a theory that enables us to calculate the effective surface
charge of colloidal particles and to efficiently obtain titration curves for
different salt concentrations. The theory accounts for the shift of pH of
solution due to the presence of 1:1 electrolyte. It also accounts
self-consistently for the electrostatic potential produced by the
deprotonated surface groups. To examine the accuracy of the theory,
we have also developed a reactive grand canonical Monte Carlo
simulations method to treat charge transfer at the colloidal surface. An
excellent agreement is found between theory and simulations, without
any adjustable parameters. I will also discuss the problems associated
with the usual constant pH simulation methods often used in the
literature.