Sour mix

is a mixer used in many cocktails, notably the Long Island Iced Tea family. It is made from approximately equal parts lemon and/or lime juice and simple syrup and shaken vigorously with ice. This produces a pearly-white liquid with a pronounced flavour. Egg white may be added as a foaming agent, to improve the texture of the finished product. Pre-mixed versions are available, and are in use in many bars - these typically consist of a powder which must be rehydrated by adding water prior to use.