CHEMlab 7

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CHEM/MBIO2360
Experiment 7. Iodine Number Determination of Triacylglycerols
2.
Iodine number calculation of Olive Oil
a)
Volume of sodium thiosulfate
= 9.9 mL – 0.0 mL = 9.9 mL = 0.0099L
b) Moles of Sodium thiosulfate
n = CV = (0.05 M)(0.0099L) = 4.95 × 10−4 mol
mole of Control
Volume of control = 36.4 mL – 11.0 mL = 25.4 mL = 0.0254 L
n = CV = (0.05 M)(0.0254 L) = 1.27 × 10−3 mol
c)
Difference between control and sample in terms of mole of sodium thiosulfate
= 1.27 × 10−3 mol - 4.95 × 10−4 mol = 7.75 × 10−4 mol
d) Gram of Iodine4
= 7.75 × 10−4 mol × 126.90
e)
𝑔
𝑚𝑜𝑙
= 0.0983 g of Iodine
Iodine number
0.0983 𝑔 𝑜𝑓 𝐼𝑜𝑑𝑖𝑛𝑒
0.1 𝑔 𝑜𝑓 𝑙𝑖𝑝𝑖𝑑
=
𝑥 𝑜𝑓 𝑖𝑜𝑑𝑖𝑛𝑒
100𝑔 𝑜𝑓 𝑙𝑖𝑝𝑖𝑑
x = 98.3 g
Iodine number of Oil sample = 98.3
Iodine number calculation of Butter
a)
Volume of sodium thiosulfate
= 31.5 mL – 9.9 mL = 21.6 mL = 0.0216L
b) Moles of Sodium thiosulfate
n = CV = (0.05 M)(0.0216L) = 1.08 × 10−3 mol
c)
Difference between control and sample in terms of mole of sodium thiosulfate
= 1.27 × 10−3 mol - 1.08 × 10−3 mol = 1.90 × 10−4 mol
d) Gram of Iodine4
= 1.90 × 10−4 mol × 126.90
e)
𝑔
𝑚𝑜𝑙
Iodine number
0.0241 𝑔 𝑜𝑓 𝐼𝑜𝑑𝑖𝑛𝑒
0.1 𝑔 𝑜𝑓 𝑙𝑖𝑝𝑖𝑑
=
𝑥 𝑜𝑓 𝑖𝑜𝑑𝑖𝑛𝑒
100𝑔 𝑜𝑓 𝑙𝑖𝑝𝑖𝑑
x = 24.1g
Iodine number of Fat sample = 24.1
= 0.0241 g of Iodine
Table 1. Iodine number of Olive oil(Oil) and butter(Fat) sample.
Oila
Fatb
3
Published Iodine Number
80-88
26-40
Experimented Iodine Number
98.3
24.1
a
Sample consist 0.1g of Olive oil b sample consists 0.1g of butter. Solution contains
cyclohexane, 1%(w/v) starch solution 10%(w/v) as titration indicator, KI solution and
Wikis Reagent (1.6% (w/v) ICl in acetic acid) and titrated with 50.0 mM sodium
thiosulfate.
As we compared our experimental values to published values, they are close enough to be
consider as ideal experimental results. However, since it cannot be in the exact value range,
we can assume that some experimental error might affect to our result.3
Abundant lipids consist fatty acid chain and glycerol backbone. Fatty acid can be saturated
and unsaturated by existence of double carbon-carbon bond.2
Saturated lipid has no double bond whether unsaturated lipid has various number of double
bonds. This unsaturated double carbon-carbon bonds make the lipid as liquid in room
temperature while saturated lipids keep as in solid. Reacting with iodine can represent the
amount of double bond in fatty acid where can react with Iodine. So If the Iodine number is
high, the number of double bond in fatty acid tail also high relatively. According to the
results from this experiment, Oil sample has more iodine value than the Fat sample.
Therefore, the Oil is more unsaturated with containing more double bonds than the Fat
sample. As we compare that physical observation of our sample, Oil is more unsaturated
lipid and has as liquid state at room temperature which also related with lower melting
point. On the other hand, Fat sample was in solid which means it contains highly saturated
fatty acid. Those fact contributes to fat lipid can have high melting point so it can keep
solid state at room temperature.
Therefore, Iodine values are consistent with our physical properties/state observation of
samples lipid.1
Reference
(1) Nichols, E.R. (2018) Biochemistry I: Biomolecules and an Introduction to Metabolic Energy Lab
Manual.
(2) Mark, B., McKenna, S. (2018) Biochemistry I Course Pack, Hayden-mcneil, Macmillan Learning,
United States of America
(3) Iodine value. (2018, November 14). Retrieved November 22, 2018, from
https://en.wikipedia.org/wiki/Iodine_value
(4) Molar mass of I2. (n.d.). Retrieved November 22, 2018, from
https://www.webqc.org/molecular-weight-of-I2.html