Stipulate a constant relative volatility . The vapor-liquid equilibrium model then becomes
An initial liquid mole fraction gives an equilibrium vapor mole fraction . Now imagine completely condensing a small sample of that vapor and using this condensate as a fresh liquid for another equilibration. Repeating this formal operation gives
These are original model calculations of ideal-stage enrichment. They are not measured compositions, a reflux design, or successive compositions of one pot undergoing simple distillation. That pot loses the more volatile component and becomes depleted; each step here instead starts from the previous enriched condensate. The displayed sequence specifies compositions, not the recoverable amount at each step.
Figure 1.
Stipulated vapor-liquid equilibrium enrichment and a separate distillation material balance
. Left: the model and formal repeated equilibration from , using complete condensation between steps. The staircase is not a reflux design or one-pot time history. Right: an independent product split with feed amount of substance and specified mole fractions. Neither panel contains measured data or a boiling-temperature curve. Details.
The algebra makes the enrichment especially transparent. With composition odds , every formal step doubles the odds, so
For every finite , , although as . This explains why repeated ideal equilibration can improve composition without making finite-step perfect separation a consequence of the model.
Simple distillation 2026-10-18
In simple distillation, pot vapor passes directly to the laboratory condenser. An initial small condensate sample can approximate vapor-liquid equilibrium with the current pot liquid. Removing enriched distillate depletes the pot's more volatile component. A collected fraction averages the changing condensate composition, rather than preserving the first-drop mole fraction.[ref]
Superheated liquid 2026-10-18
A liquid maintained above its equilibrium boiling temperature at the imposed pressure. A barrier to nucleation can delay its conversion into vapor, making this a metastable state.
Charles Thomson Rees Wilson's 1927 lecture recalls Electron cloud trails produced with X-rays in 1911, then alpha particle trails from a radium-tipped source. The improved 1912 chamber had a wide, shallow space with a suddenly falling floor to limit stirring. A roof–floor clearing electric field removed unwanted ions. Sharp photography required expansion, then the ionizing particle, then illumination.[ref]
The piston mechanism connects the space beneath the moving floor to an evacuated vessel: opening the valve lets the floor drop. Water in a trough supplies the vapor. The Smithsonian's surviving demonstration object is explicitly a 1961 replica of the 1912 apparatus.[ref]
Figure 1. . Original functional schematic, with an invented illustrative trail. Positions, sizes and delays are schematic; this is not a historical photograph or a mechanical reconstruction. Details.
After dust removal, X-rays increased droplet formation above a lower expansion threshold; larger expansions also produced dense background cloud.[ref]
The control logic separates a localized ionization trail from fog. Delays permit ion displacement and drop growth; stirring deforms the trail. A photograph alone supplies neither an absolute event time nor a calibrated particle energy.