The art of crafting cocktails places a lot of focus on the balance between flavors, including bitter, sour, sweet, salty, and umami. Flavorful ingredients like bitter liqueurs and sour citrus juice are classic, but some mixologists are digging up old-fashioned add-ins to inspire a new drinks, including ones like acid phosphate.

Most old-school American soda fountains were gone by the 1970s, and acid phosphate, used to make beverages called phosphates, was also left behind — but not anymore. This liquid is a mix of sour phosphoric acid plus mineral salts, which help temper the acidity and provide a secondary flavor-enhancing property, as most salts do.

The great thing about acid phosphate is that its sourness doesn't come with any distracting flavors, making it the ultimate neutral acid source for your drinks. To warm yourself up to it, try a Whitehall Mystery, which calls for acid phosphate with Old Tom-style gin, sloe gin, Cocchi Americano aperitivo, and Pommeau de Normandie.