A critical inorganic compound produced via chlorination, appearing as a colorless or pale-yellow liquid at room temperature with a pungent acidic odor. It absorbs moisture from air, forming fumes that consist of titanium dioxide and hydrochloric acid droplets. As the core raw material for producing metallic titanium and chloride-process titanium dioxide (TiO₂) pigment, it also serves as a key intermediate in synthesizing titanate esters, catalysts, and related compounds. Widely used in metallurgy, chemical engineering, and materials science.