Atmospheric pressure: unit of pressure equivalent to 760 torr (mm Hg).
Azeotrope: a liquid mixture of two or more substances that boils at constant temperature. The mixture cannot be separated by normal distillation, but can be redistilled and reused in its azeotropic form.
Boil up: the point at which reflux begins in the head of the still. The head temperature will rise rapidly as this occurs.
Boil up rate: The number of drops that fall from the blue drip tip in the head in 60 seconds.
Cut: a fraction of the distillate collected.
Distilland: the sample in the pot flask to be distilled.
Distillate: the final product collected after distillation.
Efficiency: a measure of the ability of the distillation column to separate compounds. This is usually referred to in theoretical plates.
Equilibration time: time required for the distillation system to come to a steady state before removal of the distillate is begun.
Equilibrium: state of which maximum vapor-to-liquid contact is achieved and the low boilers are extracted from the distilland with the high boilers remaining in the pot. This is achieved with the still in total reflux and occasionally takes many hours depending on the characteristics of the compound being separated.
Flooding: excessive amounts of liquid being forced into the head of the still because of excessively high pot temperatures.
Fraction: another name for "cut".
Fractional distillation: an intricate distillation to obtain a high purity product.
Helix: the part of a spinning band that is machined or twisted into a screw type configuration which causes the liquid in the still to be pumped downward.
Hold up: the amount of liquid required to completely wet the internal surface of the still. This is considered to be the amount of distilland that cannot be recovered from the distillation.
Packing: material placed in a distillation column to create surface on which liquid/vapor contact can take place. Common packing types include Heli-pak, Propak and may other types.
Polymerization: solidification of a liquid in the still due to the formation of large complex molecules by thermal decomposition of the initial distilland.
Rectification: enrichment of the vapor by contact and interaction with the condensed liquid.
Reflux: the liquid condensed from the rising vapor which returns to the pot flask.
Reflux ratio: ratio between the boil up rate and the take-off rate.
Take-off: distillate removed from the still in ml/minute or liters/hour.
Take-off rate: amount of distillate removed from the still in a given period of time.
Theoretical plates: unit used to measure the efficiency of the still. The theoretical plate is the contrivance which produces the same difference in composition that exists at equilibration of a liquid and a vapor. The more plates there are in a distillation column the greater the efficiency and separating ability.
Throughput: The amount of liquid that can be distilled in a given time period.
Total reflux: a condition which exists when the reflux valve is totally closed and all the condensed liquid is being returned down the column.
Vacuum: removal or evacuation of air and gas from a given space.
