seignette salt
Potassium sodium tartrate (chemical formula: NaKC4H4O6·4H2O), also known as sodium potassium tartrate, Roche salt, Rochelle salt, is a double salt formed by sodium tartrate and potassium tartrate. It is a colorless to blue-white orthorhombic crystal, soluble in water, slightly soluble in alcohol, salty and cool in taste, and slightly alkaline in its aqueous solution.