Lab+III+Distillation+-Redux


 * __ Distillation __**

**__ ﻿Introduction __** Distillation is an ancient yet widely-used method of chemical separation for liquid substances, that is still in use today. In modern times, everything from drinking water to crude oil is purified or separated using this process. To accomplish this separation, the Ideal Gas laws are used in conjunction with basic thermodynamics.

A mixture is either heated and/or put in a vacuum, and when the vapor pressure exceeds the atmospheric pressure, it will begin to boil and become a vapor. The separation occurs between compounds of different boiling points that are present in the mixture.

Though not a perfect separation, the distribution of vapor molecules will favor the compound with the lower boiling point. This vapor is then routed to a cooler area where it is can condense and pool as a liquid again. This new substance be noticeably purer than the original, with the bulk of the impurities or heavier substance left with the original receptacle.

**__ Procedure __** The procedure for the following experiment can be found at @http://greenchem.uoregon.edu/PDFs/GEMsID91.pdf

Compounds used in the following lab tests:


 * Name: Acetone
 * IUPAC Name: 2-propanol
 * CAS Number: 67-64-1
 * Molecular Formula: CH₃COCH₃
 * Compound Formula: C₃H₆O
 * Skeletal Structure:

**__ Data __** Impure acetone(ℓ) is a translucent, colorless liquid. For the initial part of the experiment the temperature of the hot plate was set to medium-low. Condensation formed on the inside of beaker when heat was initially applied, however after five minutes the condensation was no longer visible. Flask was clear without bubbles on the inside and seemed to have a slippery appearance. Condensation was noticed above the boiling pot in the bottom portion of the distillation head. The temperature was then reduced on the hot plate. Small bubbles were noticed but LabQuest™ was not started. At this point the spinner was stopped to verify boiling activity. The temperature in the distillation head was 24.9ºC.The boiling activity increased to a more visible rate: the temperature was 25.1ºC.

At 1339 the LabQuest™ was started at a rate of 2 samples per minute for 180 minutes (3 hours - the duration of the lab). The temperature of the hot plate was then increased. The observations for the distillation are as follows:


 * The temperature in distillation head declined 0.2°C, and boiling stopped, so the temperature of the hot plate was increased to restart boiling.
 * Boiling resumed for several minutes, but again began to decrease in intensity.
 * The hot plate temperature was increased as no signs of evaporation were present.
 * First condensation drops appear in receiving flask. The temperature in distillation head was 51.8ºC
 * The hot plate was turned off: 41.5 minutes had been recorded on the LabQuest™. Temperature in the distillation head was 54.6ºC
 * The boiling pot was removed from water bath.

The solution that remained in the boiling pot appeared to be a suspension of a heterogeneous mixture; the semblance was an opaque beige color. Significantly more befouled than the clear solution that was the initial mixture. The liquid in receiving flask was clear, no color, and nothing visible suspended or situated along the bottom.

**__ Analysis __** Graph A: Shows the temperature change throughout the distillation process.



Graph B: This graph shows a side by side comparison using infrared spectroscopy of the impure acetone and the resultant compound after purification.



**__ Discussion __** Data Interpretation: Graph A shows the temperature change throughout the distillation process. The LabQuest™ was started when the temperature within the distillation head reached 25ºC. From this point to approximately nine minutes, the slope of the secant line indicates a slightly positive slope, indicating an overall increase in temperature. At roughly 9 minutes, the slope changed dramatically, increasing roughly 25ºC in less than two minutes. The temperature then remained fairly constant for the duration of the distillation process. The highest temperature for the entire process was in the area of ≈ 55ºC; this fits with the higher range of the boiling point for acetone. This temperature range implies a reasonable level of purity in the acetone. Maximum efficiency was obtained by keeping the distillation rate slow and constant. For this procedure the rate was ≈ 1drop/10 sec. The each plateau indicates the boiling point of a particular liquid in the mixture. Graph B shows a side by side comparison using infrared spectroscopy of the impure acetone and the resultant compound after purification. Infrared spectroscopy is a method used to measure how molecules absorb infrared radiation and convert it to heat. In turn, this helps identify molecular structure of the test compound. Because it is necessary to understand quantum theory and quantum numbers, the interpretation of graphs A and B is largely based on deduction and speculation. The three sharp points could represent bond stretching or bending, still, they could also represent different levels of energy absorption and electron excitement. What can be inferred, however, is that for the most part the graphs are identical, and confirms that the original substance did not contain a significant amount of impurity. The depression of the spikes in the 2916-2849 cm⁻¹ range may represent the elimination of an impurity; this is also represented in the 2700 cm⁻¹ area as well. There are drastic elevations and depressions in the range of 1651-1420 cm⁻¹. This is could be due to the presence of a new impurity, possibly from the cleanliness of the lab equipment or procedural errors. All of the variations could also represent compounds that are either present or absent.

**__ ﻿ ﻿ ﻿ __****__Conclusion__** The boiling point of acetone is 56.53ºC (due to its volatile nature) and -as stated above - is one of the reasons the distillation process is helpful when needed to purify it. However, as a generalization, simple distillation is only effective when separating volatile from non-volatile substances, due to the inherent differences in those types of compounds. Without a considerable vapor pressure difference in the substances the effective separation would be dampened.

As a whole, however, simple distillation is a relatively simple and effective procedure for obtaining a rudimentary yet effective separation of liquid/aqueous solutions. It can be used for a variety of tasks to create a substance that is usable for its designated purpose, and realistically pure. For a more intense treatment, other modifications to the general procedure (such as steam or vacuum distillation) may be used to obtain the needed purity for the task. To get a substance absolutely pure, it would require another separation procedure, or a combination of various methods.

**__ Post Lab Question __** Dear Mrs. Standards,

We received your letter concerning the distillation of acetone and we feel confident that the team at Fucitol Labs can help solve your problem. We understand that pure acetone is quite expensive, running as high as $700 a ton, so your need to conserve and reuse is the first priority for us. Acetone is relatively simple to extract from paint product because of the volatility difference. As paint sits in your drums it will separate from the acetone over time, which should help expedite the process. The drums would be picked up from your facility and shipped to ours on a weekly basis. They would be transferred into a commercial size simple distillation apparatus and then the acetone can be distilled from the paint product.

The distillation apparatus consists of a large, temperature controlled boiling pot, a condenser, and a collection vat. The boiling pot is connected to an enlarged version of a West Condenser, which circulates cold water around the tubes carrying the acetone vapor. Heat is applied to the boiling pot, not exceeding 58°C. As the temperature of the solution increases, liquid acetone will begin to transition to the gaseous state, rising above the solution into the West Condenser. As the gaseous acetone progress through the condenser, it will transition back to the liquid phase prior to exiting the condenser and entering the collection vat. The heat is turned of and the purified acetone is allowed to cool to room temperature. The purified acetone is now ready to be bottled or canned and distributed back to your company. The impurities that remain from the initial solution in the boiling pot will be gathered into drums and disposed of according to EPA regulations. Accounting for error and current technological restrictions, there will be trace elements of certain impurities in the final solution. These impurities are in such small quantities that they will not adversely effect the viability of your acetone-based needs.

**__ NOTES __** The chemical structures, formulas, and vital statistics of each compound was researched using [|Wolfram Alpha computational knowledge engine] and confirmed using the [|CRC Handbook of Chemistry and Physics [90th Edition.]]