Potassium Sodium Tartrate, Tetrahydrate, Crystal, Reagent, ACS is a double salt and is deliquescent so the material deteriorates if stored in damp conditions. It has been used medicinally as a laxative. It has also been used in the process of silvering mirrors. It is an ingredient of Fehling's solution and Nylander's test, formerly used in the determination of reducing sugars in solutions. In organic synthesis, it is used in aqueous workups to break up emulsions, particularly for reactions in which an aluminum-based hydride reagent was used. As an ACS grade quality reagent, its chemical specifications are the de facto standards for chemicals used in many high-purity applications and typically designate the highest quality chemical available for laboratory use. Spectrum Chemical manufactured Reagent ACS grade products meet the toughest regulatory standards for quality and purity.