To study the Presence of Oxalate Ions in Guava Fruit at different stages of Ripening.
1. Index
Objective
Introduction
Theory
Requirements
Procedure
Observation
Chemical Equations
Calculations
Conclusion
Precautions
Bibliography
Webliography
2. Objective
The objective of this
project is to study
the presence of
oxalate ions in guava
fruit at different
stages of ripening.
3. Introduction
Guava is a common sweet fruit
found in India and many other
places which contains about 100
species of tropical shrub.
On ripening it turns
yellow in colour.
Rich in vitamin C,
this fruit is a rich
source of Oxalate
ions whose content
varies during different stages of
ripening.
It is a carboxylic acid, primarily
found in plants and animals. It is
not an essential molecule and is
4. excreted from our body,
unchanged.
Our body either produces oxalate
on its own or converts other
molecules like vitamin C to oxalate.
External sources like food also
contribute to the accumulation of
oxalate in our body.
Theory
Oxalate ions are extracted from the
fruit by
Boiling pulp with Dilute H2SO4. The
oxalate
Ions are estimated volumetrically, by
titrating the solution with KMnO4
solution.
5. Requirements
Required 100 ml. Measuring flask,
pestle and mortar, Beaker, Titration
flask, funnel, burette, weight box,
Pipette, filter paper, dilute H2SO4, N/10
KMnO4 solution, guava fruits at
different stages of Ripening.
Procedure
1. Weigh 50.0 g of fresh guava and
crush it to fine pulp using pestle-
mortar.
2. Transfer the crushed pulp to a
beaker and add about 50ml dil.
6. H2SO4 to it. Boil the contents for
about 2 minutes.
3. Cool and filter the contents in 100
ml measuring flask. Make the
volume up to 100 ml by adding
distilled water.
4. Take 10 ml of the solution from
the measuring flask into a titration
flask and add 10 ml. of H2SO4 to it.
Heat the mixture to about 60O
C and
titrate it against N/10 KMnO4
solution taken in a burette.
5. End Point: Appearance of
permanent light pink colour.
6. Repeat the experiment with 50.0g
of 1-, 2-, and 3-days old guava fruit.
Observations
7. Weight of Guava Fruit taken- 50.0 g
Volume of guava extract in titration-
10 ml
Normality of KMnO4 solution- N/10
Guava
extract
from
Burette readings Vol. of
KMnSO4
solution
used
Initial Final
Fresh guava 150 18 132
Day 1 150 15 135
Day 2 150 13 137
Day 3 150
10.8 139.2
Concordant Reading: 136.06L
9. Ionic Equation
MnO4-
+ 16H+
+ 5C2O4
2-
2Mn2+ + 8H2O + 10CO2
Calculations
1) For raw guava
N1V1 = N2V2
=>N1 x 10 = (1/10) x 132
=>1/10 x Normality of oxalate = (x/100)
= strength of oxalate in fresh guava
extract = normality x EQ. mass of
oxalate ion
= 1.32/100 x 44g/litre of diluted extract
=0.581 GL-1
10. 2)For semi ripened guava
(1 day old)
Strength of oxalate in one day old
guava extract
= (1.37/100) x 44g/litre of diluted extract
=0.603 GL-1
3) For ripened guava
Strength of oxalate in fresh guava
extract
= (1.39/100) x 44g/litre of diluted extract
= 0.612 GL-1
Conclusion
A] The normality of
oxalate ions of;
Fresh Guava: 1.32 ml
Semi Ripened Guava: 1.37 ml
Ripened Guava: 1.39 ml
11. B] Strength of Oxalate ion
in,
Fresh Guava: 0.58 ml
Semi Ripened Guava: 0.60 ml
Ripened
Guava: 0.61
ml
The content of
oxalate ions
in guava was
found
to be 59.67%,
which is close to the
literature value of 60%. It was also
noticed that the content of oxalic ions
grows with ripening of guava.
Precautions
12. 1.There should be no parallax
while taking measurements.
2. Spillage of chemicals should be
checked.
3. Avoid the use of burette having
a rubber tap as KMnO4
Attacks rubber.
4. Read the upper meniscus while
taking burette reading
With KMnO4.
5. Guava Fruit should be fresh.
6. In order to get some idea about
the temperature of the
solution touch the flask with
back side of your hand.
