A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures,[1] a scientific process of separating two or more substances in order to obtain purity.
In some cases, a separation may fully divide the mixture into pure constituents.
With a few exceptions, elements or compounds exist in nature in an impure state.
In contrast, an incomplete separation process may specify an output to consist of a mixture instead of a single pure component.
In the case of oil refining, crude is subjected to a long series of individual distillation steps, each of which produces a different product or intermediate.