A conductometric method for colloid titrations

A negative or positive colloid sample solution can be directly titrated, respectively, with a polycationic (poly-N, N-diallyldimethylammonium chloride) or polyanionic (potassium polyvinylsulfate) titrant to a conductometric end-point. With the conventional toluidine blue indicator method a positive colloid solution is titrated directly with a polyanionic titrant, but a negative colloid solution must be treated with an excess of a polycationic titrant, which is back-titrated with the polyanionic titrant. For positive colloid solutions, both indicator and conductometric methods are suitable; for negative colloids the conductometric method is preferable because of its constant titration vlues over a range of pH values.