= Paired simple and fractional distillation experiment
McMaster University's 1997/98 laboratory manual compares <simple distillation> and <fractional distillation> using charges of $25\,\mathrm{mL}$ each of <cyclohexane> and <p-xylene>. Part B uses a $100\,\mathrm{mL}$ round-bottom flask and a <fractionating column>. The protocol specifies a <boiling chip>, a heating mantle on a ring support, and the top of the <thermometer> bulb midway in the opening toward the <laboratory condenser>. Heating is adjusted for roughly one drop per second. Students record head <temperature> every $2\,\mathrm{mL}$ collected, up to $45\,\mathrm{mL}$, and plot both runs against collected <volume (thermodynamics)> on the same axes.<Chem2O06 Laboratory Manual by McMaster University/Experiment 3 procedures>[Chem2O06 Laboratory Manual by McMaster University; Parts A–B, Figure 3.5 position instruction, and Recording of Results]{ref}
Charge, atmospheric operation, and collection rate provide comparison conditions; the <fractionating column> is changed. A sharper separation of <temperature> regions would support improved fractionation. It would not directly measure product <mole fractions> or prove purity. The manual distinguishes collected <volume (thermodynamics)> from composition and states that this pair forms no <azeotrope>. No student dataset is supplied here, and the constant-<relative volatility> example is not assigned to these liquids.<Chem2O06 Laboratory Manual by McMaster University/Experiment 3 procedures>[Chem2O06 Laboratory Manual by McMaster University; Recording of Results, distinction between temperature–volume and temperature–composition plots; comparison questions]{ref}
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