A cylinder still is a type of distillation apparatus used to separate liquids based on their boiling points. It consists of a vertical cylindrical column where the liquid mixture is heated. As the mixture boils, the vapor rises through the column, allowing for the separation of different components. The design of a cylinder still allows for efficient heat transfer and vapor flow, making it suitable for producing high-purity distillates. This method is commonly used in the production of alcoholic beverages, such as whiskey and rum, as well as in the petrochemical industry for refining crude oil into various products.