4 Separation of Liquids by Fractional Distillation

4 Separation of Liquids by Fractional Distillation -...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Separation of Liquids by Fractional Distillation. Analysis of Separation Efficacy by Constructing a Volume vs. Temperature Graph and Gas-Liquid Chromatography. James Mendoza February 25, 2008 Methods and Background The purpose of this lab is to successfully distill a solution of ethyl acetate and butyl acetate, and take a gas-liquid chromatography of three different fractions of the distilled solution at different temperatures. From the distillation, an analysis of the volume of distilled liquid compared to the temperature of the liquid can be recorded. The difference between this and a simple distillation is the column. Ethyl Acetate Butyl Acetate Fractional distillation is a more useful method for isolating the individual pure liquid components from a mixture containing two or more volatile substances. The fractional distillation column is similar to that of a condenser, but it contains indentations inside the tube to hold the packing in place. Simple distillation is used to separate a volatile compound from a nonvolatile one and to separate volatile compounds from one another if their boiling points differ by at least 40-50 ºC. However, fractional distillation is used to get each volatile component of the mixture in their pure forms. Due to the packing inside of the column, the path of the vapor is significantly longer than that of a simple distillation. As the vapor from the stillpot rises up the column, some of it condenses in the column and returns to the stillpot. The condensation will get partially revaporized as it flows back down the column. With such a high column, a series of condensations and revaporizations takes place. In other terms, it is like several simple distillations occur in the column. In this distillation, due to the packing, only the most volatile of components stays in gas form until it reaches the top of the column, trying to keep the vapor at its most pure state. For this to occur, equilibrium between liquid and vapor phases must be established. The rate at which molecules in the gas phase reenter the liquid will eventually become equal to the rate at which they escape from the liquid, putting them in equilibrium. After the more volatile component has been separated through the column, the less volatile component will be heated more so that it vaporizes through the column. To index the efficiency of separation in fractional distillation, HETP is used. HETP stands for height equivalent to a theoretical plate, which is the vertical length of a column that is necessary to obtain a separation efficiency of one theoretical plate. The theoretical plate represents the single ideal distillation for each step of the distillation process. It describes the efficiency or “separating power” of the distillation, or GC column. Efficiency of each fractional distillation is then described in terms of its
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
equivalency to these theoretical plates. For a successful fractional distillation, the temperature between the top and
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/07/2008 for the course CHEM 233 taught by Professor Landrie during the Spring '08 term at Ill. Chicago.

Page1 / 6

4 Separation of Liquids by Fractional Distillation -...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online