The traditional way to get information about the polydispersity of petroleum and its fractions is the True-Boiling-Point analysis (TBP analysis). The TBP analysis is a batch distillation with a very efficient column. In the usual case (without polar components) pure components distil according to their boiling points. The plot of the temperature at the top of the column versus the mass fraction distilled is called TBP curve. This curve may be considered to be an integral continuous distribution function. If the mixture contains polar components as for example water or alcoholes azeotropy with a minimum in boiling temperature occurs. In this case the boiling-point curve is falsified and the notation TBP curve is no longer correct. Here, instead of pure components binary azeotropes leave the column. Azeotropy influences on the boiling-point curve considerably, particularly, inducing a temperature jump. In this work complex multicomponent mixtures consisting of aliphatics, aromatics and n-butanol are considered. Both the aliphatics and the aromatics form azeotropes with the alcohol, but, the aromatics within a smaller temperature range than the aliphatics. The azeotropic influence was studied experimantally and by calculation using continuous thermodynamics. In this, the work is focussed on the role of the aromatics. Particularly, the boiling-point curve and the alcohol content of the fractions distilled were investigated. The calculations are based on an infinite number of plates. This work shows, that the azeotropic influence is large even for small amounts of alcohol. In detail, this influence depends considerably on the aromatic content. Continuous thermodynamics was proved to be able to describe the boiling-piont curves as well as the alcohol content of the fractions distilled satisfactory. Small deviations from the experimental results are restricted to the location of the temperature jump. These deviations were explained to originate from the finite number of plates of the real column.