![amorphous silica amorphous silica](https://imgen2.guidechem.com/simg/product/2018/11/20/125288170104608.jpg)
Regression of experimental solubility data with theoretical equations providing for the intrinsic properties of SiOâ and the calorimetric consequences of electrostriction collapse and solvation affords close approximation of the thermodynamic behavior of aqueous silica to 5 kb and 600Â☌. Various methods to prepare and characterize each type of amorphous silica, commercial applications including principal global manufacturers, and health and safety issues are discussed. Amorphous silica is characterized by chemical composition, physical properties, and characteristics of its particles, with exact analytical procedures depending on the type and application. A discussion of microamorphous silica is presented, including colloidal silica, ie, sol or stable dispersion of discrete particles silicas gelled or precipitated from solution and pyrogenic and fused silica. Synthetic amorphous silica can be divided into microamorphous silica and vitreous silica (glass) made by fusing quartz at temperatures greater than ∼ 1700☌. Amorphous silica can be naturally occurring or synthetic, and either anhydrous or surface-hydrated with silanol groups. Amorphous silica, a three-dimensional, inorganic polymeric silicon dioxide, SiO2, does not have a crystalline structure as defined by the absence of definitive lines in X-ray diffraction measurements.