Stannous tartrate is an organotin compound with the chemical formula C4H4O6Sn. It is typically a white or off-white crystalline powder. The compound is known for its role as a polycondensation catalyst. Its primary and most significant industrial application is as a highly effective catalyst in the production of polyethylene terephthalate (PET) resin. It specifically catalyzes the esterification and polycondensation reactions between terephthalic acid (PTA) and ethylene glycol (EG). Compared to traditional antimony-based catalysts, stannous tartrate offers advantages such as higher catalytic activity, which can allow for lower reaction temperatures and pressures, and the production of PET with superior color (reduced yellowness) and thermal stability. Due to its catalytic properties, it is also explored in other polyester synthesis processes and in some surface treatment formulations. As an organotin compound, it requires careful handling with appropriate safety precautions, as some organotins are toxic.