Distillation And Purification Of Liquids Lab Report

Experiment 2: Distillation and Purification of Liquids
Angela Kaiser 100125701 ELL 308
September 19th, 2015

Introduction and Experimental: The purpose of this experiment was to determine the ratio of dichloromethane (DCM) to cyclohexane in a DCM/cyclohexane solution by carrying out a fractional distillation. The temperature and volume of distillate were measured periodically to determine the volume both components in the solution. The experiment was performed as written in “Experiment 2: Distillation and Purification of Liquids” from the Chemistry 2050 Lab Manual for Organic Chemistry Part 1, Fall 2015.

Results and Observations:
The solution of DCM and cyclohexane was clear and colourless. The following graph shows the recorded

In a simple distillation, the solution is brought to a boil and the vapours rise into a stillhead that directs them into a condenser. The vapour is condensed to the liquid phase and collected. This method works well for solutions that are composed of liquids with vastly different boiling points. However, if the liquids are similar in boiling points, fractional distillation is the preferred method of separation. In this technique, vapours are forced to pass through a fractional distillation column before reaching the stillhead. Fractional distillation columns may contain a metal sponge, or have glass projections inside the column in order to increase the amount of surface area that the vapour comes into contact with. This causes some of the vapour to condense while in the fractional distillation column. Consequently, it falls back into the liquid reservoir. However, when this liquid to the reservoir, it contains a higher ratio of the more volatile substance than it did originally. This is repeated numerous times in the fractional distillation column and each time the liquid vapourizes, the vapour increases in purity. Eventually, the vapour contains only the most volatile substance and it is condensed and

There are multiple points both at 43°C and at 72°C which indicates that liquid was collected at these temperatures. Based on this information, it would appear that two different liquids were present in solution and that one liquid has a boiling point of approximately 43°C and that the other has a boiling point of approximately 72°C. The literature value boiling point for DCM in is reported to be about 40°C and it is about 80°C for cyclohexane.
Based on the graph, DCM was collected from 4 ml to 22 ml, thus 18 ml of DCM was collected. Cyclohexane was collected from 26 ml to 35 ml, thus 9 ml of cyclohexane was collected. Therefore the observed ratio of DCM to cyclohexane was 18:9 or 2:1.
Two sources of error may have affected the experiment. Firstly, the experiment required volumes of liquid to be recorded while the vapours were distilling. It was impossible to accurately measure the volume of liquid at any given moment, as the meniscus was moving side to side. Secondly, the distillation was ended while there was still liquid in to round bottom flask. The composition and volume of this liquid were unaccounted for in the calculated