Hexafluorosilicic acid CAS 16961-83-4

Hexafluorosilicic acid, with the CAS number 16961-83-4, is an inorganic compound commonly used in various applications, particularly in water fluoridation. Its systematic IUPAC name is dihydrogen hexafluorosilicate, and it is also known by several other names, including fluorosilicic acid and hydrofluorosilicic acid.
Chemical Properties
Molecular Formula: H₂SiF₆
Molar Mass: 144.09 g/mol
Appearance: It is a colorless, fuming liquid with a sour, pungent odor.
Density: Approximately 1.22 g/cm³ for a 25% solution, increasing with concentration.
Solubility: Hexafluorosilicic acid is miscible with water, making it suitable for various aqueous applications.
Applications
Hexafluorosilicic acid is primarily used for:
Water Fluoridation: It is one of the most common agents used to fluoridate drinking water, contributing to dental health by reducing cavities.
Industrial Uses: It serves as a source of fluoride in the production of hexafluorosilicate salts and is utilized in the Betts electrolytic process for refining lead. Additionally, it is employed in wood preservation and surface modification of materials like calcium carbonate.
Safety and Handling
Hexafluorosilicic acid is classified as corrosive and can cause severe damage to tissues upon contact. It is important to handle it with care, using appropriate personal protective equipment (PPE) to prevent exposure to skin and mucous membranes.
Environmental and Health Considerations
Concerns have been raised regarding the impurities in commercial hexafluorosilicic acid, such as heavy metals like arsenic and lead. However, studies indicate that the concentrations of these contaminants are typically low and do not pose significant health risks when used in water fluoridation. The hydrolysis of hexafluorosilicates in water is rapid, leading to the formation of less harmful species, which further mitigates potential risks associated with its use.
In summary, hexafluorosilicic acid is a versatile compound with significant applications in public health and industrial processes, but it must be handled with caution due to its corrosive nature.