In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

In the Kjeldahl method for analyzing organic nitrogen content, this procedure is followed by titration of its ammonia product. VLE diagrams are used in the McCabe-Thiele method to determine the number of stages over which this process must occur. One type of these involves lowering the pressure on the system below the vapor pressure of the desired product, and is called the "vacuum" type. The Fenske equation gives the number of theoretical plates required for the "fractional" type of it. For 10 points, identify this process used to separate volatile liquids based on the differences in their boiling points.
Science