Rochelle's salt is another name for which compound?

• A. Sodium potassium tartrate
• B. Sodium potassium sulfate
• C. Potassium sodium tartrate
• D. Sodium tartrate

Answer: (A)

Rochelle’s salt is a tartrate double salt, containing both sodium and potassium. This forms the compound sodium potassium tartrate, often seen as the tetrahydrate KNaC4H4O6·4H2O. The presence of both cations is what distinguishes it from a simple sodium tartrate (which would have only sodium) or other salts like a sulfate. In clinical chemistry practice, this double salt stabilizes copper in Benedict’s (and related) reagents by forming a copper-tartrate complex, keeping copper in solution under alkaline conditions and enabling reliable detection of reducing sugars. Therefore, the best description is sodium potassium tartrate.