Dühring's rule states that a linear relationship exists between the temperatures at which two solutions exert the same vapor pressure.[1][2] The rule is often used to compare a pure liquid and a solution at a given concentration.
Dühring's plot is a graphical representation of such a relationship, typically with the pure liquid's boiling point along the x-axis and the mixture's boiling point along the y-axis; each line of the graph represents a constant concentration.