Criteria for Microscopic Stability

As defined above, microscopic stability means the absence of particle aggregation (coagulation). A sufliciently high degree of such stability is, therefore, achieved when repulsive forces between particles prevent them from collision. Of particular importance in this context is the repulsive double layer interaction that is related to the ion clouds surrounding charged particle surfaces. 

This iso-electric point is found to be one of great importance. As it is neared, the stability of the hydrosol diminishes until, at the iso-electric point, it vanishes, and coagulation or precipitation occurs, the one or the other according to whether the concentration of the proteid is high or low, and whether the isoelectric point is reached slowly or quickly, and without or with mechanical agitation. 

Derjaguin and Landau (1993) derived a criterion for stability for strongly charged spheres 1) from the mathematical description of the inter- 

Schulze (1882, 1883) which were reviewed and extended by Hardy (1900) and led to the Schulze-Hardy rule  

This agreement with empirical data facilitated the quick acceptance of the DLVO theory within the colloidal community. 

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