Performance Of Modified Schulze-Hardy Rule On The Stability Of Nano, Micro, And Macro Colloidal Dispersions: A Comprehensive Account

The Schulze-Hardy (S-H) rule that explains the precipitation (flocculation/coagulation) of colloid particles is almost 125 years old. This rule states that counter ions of the electrolytes are responsible for the precipitation of the charged colloids, and the charge on the counter ion determines the amount of the electrolyte required for the event. Though this is necessarily true, it does not take into account various other variables in the system viz. charges on the co-ions, the ionic strength of the solution, the charge density on the interacting ions, and that of the colloid particles, shape of the particles, etc. In this article, we have modified the S-H rule taking into account some of the above mentioned variables viz. the ionic strength of the solution, the charge density of the interacting ions as well as that of the associated colloid particles. We have attempted to find out the validity of the modified S-H rule on the nano, micro, and macro colloidal systems so far remaining unreported in the literature.