Generally, SiO₂ were disliked in natural water suspension solutions and various methods of its exclusion have been investigated in industrial fields.
In colloid science, SiO₂ of the nascent state in water solution is well known as a hydrophilic inorganic sol, and also has negative charge in weak acid, neutral solution and alkali solution. Clay and arsenic trisulfide particles in water solution have the properties of negative charge and hydrophobic sol. In the above cases, the suspension expects to appear phenomena of the sensitization with mutual action according to control the concentration of hydrophilic sol on hydrophobic sol in the disperse system.
In the experiment, it was investigated that the effect of coagulation by this sensitization of As₂S₃ and clay with SiO₂ were calculated by using C₀⁶⁰ radioactive isotope method, and moreover, in its coagulation state observed by electromicroscope.
The coagulation effects of the sensitization of SiO₂ sol against clay suspension were much weaker than the electrolytes in industrial water or natural water comparing the action of coagulation of electrolyte （Al₂(SO₄）₃) with non-electrolyte (SiO₂), and the effect of coagulation by SiO₂ concluded in this research to be caused by only van der Waals’forces and not Coulomb's forces.