Question

Why automatic titration is most accurate than manual titration

Answer 1

Modes of titration

            Titrations are performed manually point by point, or automatically, where the titrant is introduced continuously (monotonically or dynamically). In modern analytical chemistry automation is of increasing importance. Automation of a point-by-point titration is seldom trivial. Kinetic factors concerning the chemical reaction and the response of the indicating system are of paramount importance. Cell configuration, stirring, positioning of end-point detector and of input of titrant are to be considered for ensuring high accuracy.

            Equilibrium throughout the titration curve can be attained only when the titrant is added at an infinitely low rate. Two factors determine the rate at which a potentiometric curve approaches the state of equilibrium: the kinetics of the chemical reaction and the kinetics of the electrode process. Both factors are slowest in the vicinity of the equivalent point (why?), the region with utmost importance, from which the end point is determined (Fig.1-1a). (In conductometric titrations, on the contrary, the region around the end point is of no analytical importance; the end point is determined by extrapolation from the left and right branches of the titration curve away of the end point). At faster titration rates compared to the kinetics of the system, a delayed end point is obtained (Fig.1-1b).