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
Examiner
teacher 3
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….. 5
INTRODUCTION 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 6
Bengal and Nilgiri Hills. A cup of Indian tea contains 80mg of caffeine which is the indispensable content of tea.
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 7
obtained from the decaffeination of tea dust and also from coffee. 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 1. ROUND BOTTOM FLASK.
2. BUNSEN BURNER, MATCH STICK.
3. BEAKERS. (250ml AND 75 ml)
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CHEMICALS REQUIRED 1.Basic Lead Nitrate
2. Lead Oxide
3. Chlofororm
4. Distilled water
5. Animal Charcoal
6. Dilute Mineral Acid
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Procedure 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.
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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. 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. 12
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.
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 CAFFEINE PERCENTAGE TASTE THE TEA CONTENTS COMPOSITION VARIETY RED LABEL
0.029
0.0725%
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MILD AND SOOTHING
TAJ MAHAL TATA TEA LIPTON
0.05
0.0125%
0.036
0.09%
0.047
0.1175%
SLIGHTLY STRONG
STRONG PLEASANT
VERY STRONG
INFERENCE FROM THE CAFFEINE CONTENT AND THE TASTE OF THE TEA AS DESCRIBED ABOVE SHOWS THAT THE GREATER THE AMOUNT OF 14
CAFFEINE, THE BITTERNESS AND STIMULATING EFFECT OF THE TEA.
Bibliography 1. Help from internet. 2. Information from library. 15
