chemistry investigatory project on the topic : to determine percentage of caffeine in different tea...
DESCRIPTION
to determine percentage of caffeine in different tea samplesTRANSCRIPT
CHEMISTRY INVERSTIGATORY PROJECT Name: JYOTI DOGRA
Class: XII-b
School: K.V.NO.1
INDEXINDEX CERTIFICATE. ACKNOWLEDGEMENT. AIM. INTRODUCTION. APPARATUS & CHEMICALS
REQUIRED. PROCEDURE. OBSERVATION. INFERENCE.
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KENDRIYA VIDYALAYA
MALKAPURAM VSP-05
CERTIFICATE
Certified by the DEPARTMENT OF CHEMISTRY that it is a bonafied
project conducted by
JYOTI DOGRA
Of CLASS XII-A
During the ACADEMIC YEAR 2012-13 conducted by AISSE, NEW
DELHI.
Signature of external Signature of chemistry
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Examiner teacher
ACKNOWLEDGEMENT
I owe my thanks to our principal
for providing laboratory facilities.
And a tone of thanks to
for his valuable guidance and providing the required apparatus to perform my
project work.
And a lot of thanks to my friends, classmates and family members who encouraged me in doing this project
successfully.
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AIM
TO DETERMINE THE PERCENTAGE
OF CAFFEINE IN DIFFERENT
SAMPLES OF TEA…..
INTRODUCTION
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Tea is a highly popular drink all over the world. A cup of tea is often taken as a mind-freshner. This can be primarily
attributed to the presence of a stimulant called CAFFEINE in the tea. Besides this tea also contains various polyphenolic compounds that act as
flavourings agents. Relative contents of these compounds result in different
varieties available under different brand names.
The quality of tea leaves also greatly influence of the taste of the tea.
Tea is popular name of the tropical plant whose botanical name is Camellia thea.
India is the largest producer of good quality tea and it is mainly grown in
slope of hills of Assam, West Bengal and Nilgiri Hills. A cup of Indian tea contains
80mg of caffeine which is the indispensable content of tea.
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Caffeine is a nitrogenous organic compound of alkaloid group. These
groups of substances have a marked physiological effect on the human body
when taken in considerable amount. It is widely used as a stimulant of the central nervous system and also has hypotonic and sleep inducing effect. Pure caffeine
has the general formula C8H10N402. IUPAC name of this substance is 1, 3, 7-
trimethyl xanthamine.
It occurs as a white powder that melts at around 2380C. It is fairly soluble in hot water and on cooling the solution gives
crystals made up of caffeine monohydrate. In this case the compound is less soluble in organic solvents than in hot water. It is odorless but even a small amount have a very bitter taste. Caffeine
is the main flavoring agent in the tea leaves. It is obtained from the
decaffeination of tea dust and also from coffee.
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It exerts a simulative effect on the cerebral cortex but later has a
depressant and narcotic action. It is also useful in cardiac dropsy. An abnormal
sate arising from caffeine is callrd caffeinism. The main symptoms are
nervousness, Insomnia and Tachycardia. It is used in medicines
in the form of chlorides and nitrates.
In this project we will do a careful study of different brands of tea and
will extract and carefully analyze their caffeine content. The result
would thus tell the exact content of caffeine present in different samples
analyzed.
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APPARATUS REQUIRED
CHEMICALS REQUIRED9
1. ROUND BOTTOM FLASK.
2. BUNSEN BURNER, MATCH STICK.
3. BEAKERS.(250ml AND 75 ml)
Procedure10
1.Basic Lead Nitrate
3. Chlofororm
5. Animal Charcoal
2. Lead Oxide
4. Distilled water
6. Dilute Mineral Acid
TEA LEAVES OF THE
FOLLOWING
VARIETIES
In a litre round bottom flask 40gm of first sample was taken.
To this about 250ml of distilled water was added and the contents were refluxed for about an
hour. The brown colour extracted is separated by decantation followed by filtration when still hot.
Lead acetate is dissolved into water in 250ml beaker.
The solution is boiled and the lead oxide is added slowly to the boiling solution with
constant stirring. It is filtered and again boiled.
The filterate thus obtained is added dropwise to this extract till no precipitation occurs.
The filtrate is treated with animal charcoal to decolourise extract.
The clear solution is extracted with 100mg of chloroform after separating by filtration.
The total solution is taken into distillation flask to remove the solvent by distillation.
The residue left in the flask is dissolved in minimum amount of hot water and the dissolved
contents are transferred to the boiling tube. The solution is kept for slow crystallization.
When the white crystalline solid comes out of the solution it is filtered, dried in desiccators and
weighed. The above procedure is repeated for all samples
of tea.
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The observations are carefully recorded.
The chemistry involved in the experiment is as follows:
Caffeine being soluble in water goes into the solution on refluxing.Lead oxide when added to lead acetate solution helps lead to precipitate and come out in the form of insoluble lead sulphate as it is a basic oxide.The activated charcoal adsorbs the coloured pigments from the brown coloured solution.Chloroform is used for extracting the caffeine as it is a more soluble in CHCl3 than in cold water.On boiling caffeine being more volatile evaporates leaving a white mass behind.
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On adding more chloroform and by gradual evaporation we get nice crystalline caffeine.OBSERVATION
About 49gm of each sample was taken. The contents of caffeine of the samples were noted and their presence in terms of percentage was calculated.
NAME OF THE TEA VARIETY
CAFFEINE CONTENTS
PERCENTAGE COMPOSITION
TASTE
REDLABEL
0.029 0.0725% MILD AND SOOTHING
TAJ MAHAL
0.05 0.0125% SLIGHTLY STRONG
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TATA TEA
0.036 0.09% STRONG PLEASANT
LIPTON 0.047 0.1175%VERY STRONG
INFERENCEFROM THE CAFFEINE CONTENT AND THE TASTE OF THE TEA AS DESCRIBED ABOVE SHOWS THAT THE GREATER THE AMOUNT OF CAFFEINE, THE BITTERNESS AND
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STIMULATING EFFECT OF THE TEA.
Bibliography
1. Help from internet.
2. Information from library.
3. Help from
teachers.
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JYOTI JYOTI DOGRADOGRA
xii-bxii-b