A sodium-potassium alloy is a metallic mixture primarily composed of the elements sodium and potassium. This alloy is known for its low melting point and high reactivity, making it useful in various applications, including as a heat transfer medium in certain types of nuclear reactors. The alloy typically contains around 78% sodium and 22% potassium by weight. Due to its properties, it can efficiently transfer heat while remaining liquid at lower temperatures compared to pure metals. However, its reactivity with water and air requires careful handling and storage to prevent hazardous reactions.