Hexamethyldisiloxane is one of the most fundamental and important members of the organosilicon family. Its chemical formula is C₆H₁₈OSi₂; it has a molecular weight of 162.38 and is identified by CAS number 107-46-0. Within the IOTA product portfolio, it corresponds to the grade IOTA 005. It is a colorless, transparent liquid with a density of approximately 0.764 g/cm³ (at 25°C), a boiling point of 99.5–100.5°C, and a flash point of only -1.1°C, classifying it as a flammable liquid. While insoluble in water, it is miscible with various organic solvents and exhibits excellent chemical stability. The core structure of hexamethyldisiloxane consists of two trimethylsilyl groups linked by an oxygen atom (Me₃Si-O-SiMe₃); this simple molecular architecture imparts unique physicochemical properties. In the organosilicon industry, it serves as both a vital intermediate and a key raw material for a wide range of organosilicon products. From silicone oil and rubber production to pharmaceutical synthesis and analytical reagents, hexamethyldisiloxane finds applications across multiple stages of the organosilicon industry chain. Understanding this fundamental compound serves as the starting point for comprehending the entire world of organosilicon materials.