fractional distillation

Fractional Distillation Page 1

I. EXPERIMENT TITLE : Fractional Distillation

II. EXPERIMENT DATE : April 30th , 2015 at 7.30 p.m

III. END OF THE EXPERIMENT : April 30th , 2015 at 10.00p.m

IV. EXPERIMENT PURPOSE :

- Determine refractive index of distillate

- Determine purify of distillate

V. BASIC THEORY

DISTILLATION

Distillation is process of heated liquid until its boiling point reached,

then flow the vapor into condenser and collected the condensed vapor as liquid

substance. The aim of distillation is to purify the liquid substance which is has

different boiling point. Fractional distillation is the separation of a mixture into its

component parts, or fractions, such as in separating chemical compounds by their

boiling point by heating them to a temperature at which one or more fraction of the

compound will vaporize. Simple distillation can be used to separate components of a

mixture that have a large difference in their boiling points. If two components have a

boiling point difference of less than 40-50oC, simple distillation will not be successful

at separating them. In this case, fractional distillation must be used. When two

compounds with relatively close boiling points are heated, the vapor above the liquid

will be composed of both components at the boiling point. Consider the simple

distillation of a mixture of 50:50 A and B, where A has a lower boiling point than B.

When the mixture begins to boil, the vapor will be richer in A, but still have a

significant proportion of B; lets say the vapor above the boiling liquid is 66:33 A:B.

This vapor would get cooled in the condenser and drip into the receiving flask. At the

end of the simple distillation the receiving flask has been enriched in A and the liquid

remaining in the still pot is enriched in B. To purify A you would take the liquid from

the receiving flask composed of 66:33 A:B, set up another simple distillation,

enriching to perhaps 80:20 A:B. After a series of these vaporization/condensation

cycles you would finally get pure A. Fractional distillation can be considered a series

of simple distillations but rather than having many condensers and receivers, the

evaporation/condensation cycles take place in a single distillation column. Distillation

columns are high surface area tubes that allow multiple vaporization/condensation

cycles to occur at once. The added surface area in the column can come from glass


protrusions like in Vigreux columns, the ones we will be using, or from a packing

material such as glass beads or steel wool put in a hollow tube which is known as a

Hemple column. In fractional distillation, vapor rises up the column and condenses on

the packing, then re-evaporates, rises further up the column and condenses again. This

evaporation/condensation continues up the column and with each cycle the vapor

becomes more and more pure in the lower boiling component. In this way, fractional

distillation accomplishes in one apparatus what would require several simple

distillation setups. The more vaporization/condensation cycles that the mixture goes

through, the better the separation. Although more surface area in the column leads to

better separation, it also makes the distillation process slower. Additionally, surfaces

in the column will be covered with condensation, and liquid that sticks to the surfaces

will not be distilled. The liquid condensed on the surfaces in the column is known as

hold-up. When using fractional distillation chemists try to strike a balance between

the quality of the separation and the speed of the distillation. During fractional

distillation there is a temperature gradient over the length of the column. The boiling

point of a mixture varies with the composition of the mixture; the higher the

percentage of the low boiling component, the lower the boiling point will be. Thus as

the mixture travels up the column and becomes purer, the temperature of the column

decreases. When the distillate finally reaches the still head, the thermometer reading

begins to rise. The thermometer reads the boiling point of the vapor that is condensing

on it. (Boiling point and condensation point are the same temperature.) If the

thermometer reads at the boiling point of the lower boiling compound, the distilled

liquid is pure. When the temperature rises above the boiling point of the low boiling

compound that means more and more of the high boiling component is starting to

distill over. To ensure a temperature gradient over the column, the still pot should be

heated slowly. Most of the vapor from the boiling still pot should condense and drip

back down into the still pot, a process known as refluxing.

If one compound is much more volatile than the other, the compounds

can be separated in one evaporation step. Such a step is called simple distillation and

uses an apparatus that consists of only a pot, a distillation head, a condenser, an

adapter, and a receiver. When the boiling points of two compounds differ by less than

40 C, they cannot be separated efficiently by simple distillation. Fractional

distillation, a process that has the effect of many simple distillations, must be used. A


fractional distillation apparatus includes a fractionating column or a Vigruex column

placed between the pot and the distilling head

At this experiment we use spirit which is has 85% composition of

methanol. Methanol has 64,70C and refraction index 1,3284.Because distillation is a

separated method based on difference of boiling point of component. There is two

step of distillation that is boiling process and condensed process. Boiling point of

substance was effect by interaction inter-ionic, van der waals, dipole-dipole

interaction, and hydrogen bonding. Pressure and vapor composition can be determined

if the pressure and vapor composition of the purify substance has been known, based

on the Raoult law.

METHANOL

Methanol is a colorless volatile liquid with a faintly sweet pungent odor

similar to ethyl alcohol. The substance is fully soluble in water. Vapors of methanol are

slightly heavier than air and may travel some distance to a source of ignition and flash

back. Accumulations of vapors in confined spaces such as buildings or sewers may

explode if ignited. There is potential for containers of liquid to rupture violently if

exposed to fire or excessive heat for sufficient time duration. Methanol is listed as a

Poison-Class B. It is harmful if swallowed or absorbed through the skin. Ingestion of

as little as one ounce can cause irreversible injury to the nervous system, blindness, or

death. It cannot be made nonpoisonous. Causes eye and respiratory system irritation


and may cause skin irritation. Avoid liquid, mist, or vapor contact. Vapor inhalation or

liquid penetration of the skin can cause central nervous system depression.

Physical and Chemical Properties

Physical Form: ............................................Liquid

Color: ..........................................................Colorless

Odor: ...........................................................Faintly sweet pungent odor like ethyl

alcohol

Boiling Point:..............................................148o F at atmospheric pressure

Melting point:..............................................-144o F

pH:...............................................................7.2

Solubility:....................................................100%

Specific Gravity: .........................................0.792 (@ 68o F)

Vapor Density: ............................................1.11 (@ 60o F)

Vapor Pressure:...........................................1.86 psia (@ 68o F)

% Volatile by Volume: ...............................100

Molecular Weight: ......................................32.04

Density: .......................................................6.63 lb. per gallon (@ 60o F)

Critical Temperature:..................................464o F

Critical Pressure:.........................................1142 psia


VI. TOOLS AND MATERIALS

A. Tools

Electric stove

Pipe

Test Tube

Refraction meter

Distillation Flask

Liquefier

Thermometer

B. Materials

100 mL spirit

Methanol 95%

Methanol 80%

Methanol 70%

Methanol 60%

Methanol 50%

Methanol 40%

Methanol 30%

Boiled stone


VII. FLOW CHART

-

- Calculate % purify of

distilate % purify of destilate

Methanol

95%

Methanol

70%

Methanol

30%

Methanol

80%

Methanol

60%

Methanol

50%

Methanol

40%

-Measure

Calculate fraction index with refratometer

Compare with

-Put into destilation flask

-Heat until 64,5oC

100 mL spiritus

100 mL Destilate


VIII. DATA OF EXPERIMENT

No. Procedure Data of Experiment

Hypothesis/Reactions Conclusion Before After

1.

Spiritus: light

purple solution

Methanol 95% :

colorless solution

Methanol 80% :

colorless solution

Methanol 70% :

colorless solution

Methanol 60% :

colorless solution

Methanol 50% :

colorless solution

Methanol 40% :

colorless solution

Methanol 30% :

colorless solution

Distillate :

colorless

% average

purify of

distillate

86,6774%

Boiling point of

methanol 64,5%

Purify of

distillate

86,6774%

- Calculate % purify of distilate

% purify of destilate

Meth

anol

95%

Meth

anol

70%

Meth

anol

30%

Meth

anol

80%

Meth

anol

60%

Meth

anol

50%

Meth

anol

40%

-Measure

Calculate fraction index with

refratometer

Compare with

-Put into destilation flask

-Heat until 64,5oC

100 mL spiritus

10 mL Destilate


IX. EXPLANATION

Distillation is a separation method based on difference of boiling point of

component or based on the rate or the easier vaporization of the substance as we

known as volatility compound, for example is methanol, hexane, chloroform, and

acetone. At this experiment, we want to determine refractive index of distillate and

determine percentage purify of distillate. So, first we filled 100 mL of spirit which is

has light purple color of solution into distillation flask, then we set the apparatus like

picture below, we heated and we added boiling stone at the distillation flask to make

the heat even on the solution, then we waited it to produce distillate. And distillate

that is produce methanol, because spirit was contained by methanol and water.

Methanol which is has boiling point 64,70C and water has 100

0C, so methanol will

vapor first and condensed become condensed vapor or distillate. And it is the reason

why temperature of distillation should keep on 64-650C. At this step we know that the

atmosphere pressure is same with methanol pressure, so methanol will vapored and

water still on liquid phase at distillation flask because when the temperature shown

number 64,70C water was not vapored.

Fractional Distillation Apparatus set on

experiment

Fractional Distillation

Apparatus set on theory


The methanol vapor will be condensed into condenser which is flowed with

water as cooler, then the methanol vapor will be methanol condensed vapor and

become at liquid phase then flowed into measuring glass.

While we waited for it, we determine the refractive index with refraction

meter. First we tested the methanol 95%, methanol 80%, methanol 70%, methanol

60%, methanol 50%, methanol 40%, and methanol 30%. From our group observation

we get Refractive index of

30% methanol: 1,33404

40% methanol: 1,34050

50% methanol: 1,34160

60% methanol: 1,34510

70% methanol: 1,34160

80% methanol: 1,34370

95% methanol: 1,34680

There was a fault at data refractive index of 60% methanol, it should be not

too great but is too great then it make the refractive index of 70% methanol until 80%

methanol was smaller than 60% methanol.

Spirit has purple light color Spirit has purple light color


At this experiment we take 3 test tube sample of distillate, each test tube filled

by 10 mL of distillate. The distillate has colorless solution and the odor was alcohol

characteristic.

First distillate has difference refractive index with second distillate and third

distillate because at first distillate the temperature was smaller than second and third

distillate. It make the distillate that we got will be purifier at first distillate. We can

explain it with the difference boiling point of methanol and water that contained in

spirit. When the temperature was more increase or bigger than 650C or approach

1000C, the distillate that produce will be contain by water too, not just methanol. Then

after we take three sample of distillate we test it with refraction meter to know the

refractive index of the distillate. And the refractive index of sample distillate is:

First sample: 1,34475

Second sample: 1,34685

Third sample: 1,34365

And the average of refractive index sample is 1,34508, so we can compare the

distillate that we got in the range of 80% methanol and 95% methanol. We count the

% purify of distillate with the function below:

% purify of distillate =

( ( ) ( )

( )

The distillate has colorless

solution

The distillate has colorless solution


We got % purify of distillate was 86,6774.%, it mean that the distillate contain by

86,6774% methanol and the other substance 13.3226%. And based on the theory that

we got we know that the methanol which is contained on spirit was 85% methanol. It

was close with our experiment result. So, we can say that our experiment result was

right.

X. DISCUSSION

There is no From this experiment that we have committed there are based on

the theory. And there are no errors in our experiments.

XI. CONCLUSION

Based on the experiment that we got, we can conclude that:

a. The average refractive index of distillate is 1,34508

b. The purify of distillate that we got is 86,6774 % it was close with theory that

we got that is 85%.


REFERENCES

Anonymous. 2001. Methanol-MSDS.pdf.

(online).(http://terranitrogencorporation/methanol-msds.pdf , accessed

May 17, 2015 at 7.52 a.m.)

Anonymous. 2007. MATERIAL SAFETY DATA SHEET-Brandspiritus 85%.pdf.

(online).(http://hbvchemicalien.nl , accessed May 17, 2015 at 8.15 a.m.)

Anonymous. 2008. Experiment 6 - Simple and Fractional

Distillation.pdf.(online).(http://chemistry.about.com/exp.6.1.pdf ,

accessed May, 9 2015 at 9.23 a.m.)

Anonymous. 2015. Fractional Distillation.pdf (online).

(http://www.nvcc.edu/stb/chm/45_fractdist.pdf, accessed May, 9 2015 at

7.18 a.m.)

TimPenyusun .2015. Panduan Praktikum Kimia Analitik II: DDPK. Surabaya:

Jurusan Kimia FMIPA Unesa

Underwood,A.L dan Day.R.A.Jr.2002. Analisis Kimia Kuantitatif Edisi Keenam.

Jakarta: Erlangga

Wright, B. F. 2001. Distillation of Alcohol and De-

Naturing.pdf.(online).(http://www.distillationgroup.com/distillationofalco

holandde-naturing.pdf , accessed at May 9, 2015 at 7.13 a.m.)

Surabaya, May 18th

, 2015

Mengetahui,

Dosen/Asisten/Pembimbing, Praktikan,

(.) ()


Attachment

Spirit with light purple

color of solution

Methanol 30%, colorless

solution


solution


solution


solution


solution



solution


solution

Setting the apparatus of distillation The temperature of

distillation was 64,50C

Distillate produce is

colorless solution

Three test tube which is filled with

distillate 10 mL


CALCULATION

Given :

Refractor index of

30% methanol = 1,33404

40% methanol = 1,34050

50% methanol = 1,34160

60% methanol = 1,3451

70% methanol = 1,34160

80% methanol = 1,34370

95% methanol = 1,34680

Sample I = 1,34475

Sample II = 1,34685

Sample III = 1,34365

Asked : % purify of distillate ?

Answer :

- Average refractor index of sample =

=

= 1,34508

- Botton Limit = 80% methanol

- Upper Limit = 95% methanol

- % purify of distillate =

( ( ) ( )

( )

= ( ) ( )

( )

= ( )

+80%

=

= 6,6774 + 80%

= 86,6774 %

fractional distillation

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