Practicum of Sublimation - Science Laboratory 2 Courses - IPSE FPMIPA UPI Assignment
SCIENCE LAB 2
Sublimation Practice
A. Date : September 18, 2017
B. Tittle : Sublimation
C. Objective : To
separate camphor from contaminator using sublimation process
D. Basic
Theory
Purification of
some organic compounds may frequently be achieved by the technique of
sublimation as an alternative. The success of the method depends upon the
compound having a high enough vapour pressure at a temperature below the
melting point, so that the rate of vaporization from the solid will be rapid
and the vapour may be condensed back to the solid upon a cooled surface.
Impurities should have materially different vapour pressure to the compound
undergoing purification so that they may be either removed with the initial
sublimate or allowed to remain in the residue.
The yield of
sublimation will be greatly improved if the sublimation is carried out under
reduced pressure, and further under these conditions to lower temperature
employed reduces the possibility of thermal degradation. The process should not
be hurried, either by raising the temperature too rapidly in the initial stages
or by using finally too high temperature. As a general guide, the temperature
should be in the region of 30ᵒC
below the melting point of solid or lower if sublimation takes place reasonably
smoothly. (Furniss, B.S, et al, 1989)
Sublimation is a unit operation that could receive much greater attention in the future as a purification method. From a frequent batch process used for simple separation of a desired volatile constituent from a non-volatile impurity, sublimation can progress to continuous, multistage methods for fractionating materials of differing volatility on a large industrial scale. This would be particularly important for materials that decompose at temperatures below the melting point and that have low solubility in common solvents. More experimental information, particularly as regards the factor influencing the condensation of solid from the vapour, would be of value in design of equipment. (A. Holden, 1968)
E.
Materials and Equipments
1.
Materials :
1. Contaminated camphor
2. Water
3. Aluminium
foil
4.
Equipments :
1.
Balance
(1 set)
2.
Watch glass (1)
3.
Tripod (1 set)
4.
Beaker glass 100 mL (1)
5.
Wire gauze with asbestos centre
(1)
6.
Round-bottom flask 100 mL
(1)
7.
Spatula (1)
8.
Matches (1)
9. Aquadest bottle (1)
F.
Observation
Table
|
No |
Procedure |
Observation |
|
1. |
Separation of camphor ( C10H16O
) from contaminator Ø Contaminated camphor powder is weighted by using balance
and watch glass
Ø The contaminated camphor powder is placed in 100 mL
beaker glass by using spatula
Ø 50 mL of water are added into 100 mL round-bottom
flask by using aquadest bottle
Ø Beaker glass is placed on the wire gauze which
already placed set up on the tripod
Ø Bunsen burner is placed in the centre of tripod
Ø 100 mL round-bottom flask filled with 50 mL of water
is placed on the surface of 100 mL beaker glass until the beaker glass’
surface is covered
Ø The holes around the outer circle of beaker glass
are plugged by aluminium foil
Ø The bunsen
burner is turned on by using matches and set up to be small fire
Ø The fire is turned off and round-bottom flask is
picked up by using tissue
Ø The crystals are collected by using spatula, placed
on watch glass, and weighted by using balance
|
·
1 gram of
contaminated camphor powder ·
The initial colour
of contaminated camphor powder is black
·
Its colour is
still black
·
The
temperature of water is in room temperature
·
The
contaminated camphor powder get burn ·
The colour of
powder slowly turn white ·
By time, the
bottom of the flask has visually something like dew ·
The colour of
substance in beaker glass turns black again
·
There are some
crystals on the bottom of the flask ·
The colour of
crystals is white ·
The colour of
substance in beaker glass is black burnt ·
The colour of water
is still colourless and the temperature is a bit warmer
·
0.126 gram of
crystal gotten ·
The shape of
crystals is star look alike
|
G.
Analysis
Data and Discussion
Ø Analysis data
At
first, we do the calculation to determine mass of crystal and mass of the black
substance:
Known:
Initial
mass of contaminated powder: 1 gram
Mass
of crystal: 0.216 gram
Question:
Mass of the black substance?
Answer:
Initial
mass of contaminated camphor powder = Mass of crystal + Mass of the black
substance
1
gram = 0.216 gram + x
X
= 1 gram – 0.216 gram
= 0.784 gram = Mass of black substance
So, the mass of black substance left in beaker glass is 0.784 gram.
Ø Discussion
The black substance which had been
mentioned above is carbon and mixed with the pure camphor that has original
colour of crystal white. Carbon and camphor may have different vapour pressure
which camphor has lower vapour pressure than carbon, so the camphor could
sublimate and separate from the contaminator, carbon, or residue and becomes pure
camphor (the crystal).
After measurement, we got 0.216 gram
of crystal or pure camphor. Because we don’t do the measurement for the residue
to make sure the mass of it due to limited time and number of balance set, we
just do the math to determine the mass of carbon or residue. It is quite
confused and insecure at first because we don’t know the ratio of carbon and
pure camphor before mixed. So, it is a bit hard to know if the result of
crystal is in normal or expected mass of crystal after the experiment. But, at
least, we can assume by the colour of initial powder which is visually almost
completely black, so the carbon is much more than pure camphor and it can make
the gotten result of crystal’s mass and the mass of residue just right and
reliable.
And also, not just because we didn’t
actually do the real measurement using balance to determine the mass of
residue, the less mass of crystal can be predicted occur because we picked up
the flask three times to see if the sublimation had already started and checked
the amount of crystal on the bottom of flask to see if the sublimation had
stopped which could be known if there were no addition of crystal from the
amount of crystal since the last checked up. The repeated pick up during the
heating may influence the amount of crystal in the end. Because since the holes
are covered by the aluminium to prevent any heat flowing out the system which
can impact factors such as temperature, vapour pressure, and possibility of
sublimation, the repeated pick up might also cause the heat flowing out and
influence temperature which impact pressure which impact the possibility of
sublimation. Because if we want higher possibility of sublimation, we should
have high temperature to get high pressure. And the repeated pick up cause the
substance couldn’t get maximum heat to do maximum sublimation and this analysis
can be the fact of why we got few amount of crystal or pure camphor.
And for the water in round-bottom
flask, because we didn’t use thermometer, then we assumed that initial
temperature of water followed the room temperature. And because we also didn’t
use thermometer to measure the temperature of water after heating. It just can
be known by touch. When picking up the flask which made of glass, the flask was
felt warmer because of the heating and it can be assumed that so was the water.
H.
Conclusion
After all, we can conclude that
sublimation technique can be used as the method to separate impurity mixture
and in the experiment, we get 0.216 gram of crystal or pure camphor and 0.784
gram of contaminator or residue or carbon. This technique is quite simple to
applied and give good experimentally result of pure substances as expectation
based on either theoretically or formulated calculation.
I. References
Furniss, B.S, Hannaford, A.J, Smith, PWG, and Tatchell, A.R.
(1989). Vogel's textbook of Practical
Organic Compound. Longman Group: UK
A.Holden,
Claire, and Howard S. Bryant. (1968). Purification
by Sublimation. Taylor &
Francis Group: England
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