PIYUSH

CLASS XII-SCIENCE

ROLL NO. - 9123850

CHEMISTRY PROJECT-CAFFEINE IN TEA SAMPLES

ACKNOWLEDGEMENTS

I would like to thank my teachers Mr. JITENDRA TIWARI and Mr. SANJAY GAYAKWAD for their support who helped me in completing my project on the TOPIC – DETERMINATION OF CAFFEINE IN TEA SAMPLES

PIYUSH

CERTIFICATEThis is to hereby certify that, I student of class XII Science completed my project work on the topic DETERMINATIONOF CAFFEINE IN TEA SAMPLES under the guidance of my teachers.

SIGNATURE

(subject teacher)

AIMDETERMINATION OF CAFFEINE IN TEA SAMPLES

INTRODUCTIONTea 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.

 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 2380 C. 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 dustand also from coffee.It exerts a simulative effect on the cerebral cortex but later has a depressant and narcoticaction. It is also useful in cardiac dropsy. An abnormal sate arising from caffeine is called 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 .

APPARATUS REQUIRED

1. ROUND BOTTOM FLASK.2. BUNSEN BURNER, MATCH STICK.3. BEAKERS. (250ml AND 75 ml)

CHEMICALS REQUIRED

1. Basic lead nitrate2. Lead oxide3. Chloroform4. Distilled water5. Dilute mineral acid

INDEX

1. ACKNOWLEDGEMENT2. CERTIFICATE3. AIM4. INTRODUCTION5. APPARATUS AND CHEMICALS REQUIRED6. PROCEDURE7. OBSEVATION8. INFERENCE

Procedure  

1. In a litre round bottom flask 40gm of first sample was taken.

2. To this about 250ml of distilled water was added and thecontents were refluxed for about an hour.

3. The brown colour extracted is separated by decantationfollowed by filtration when still hot.

4.Lead acetate is dissolved into water in 250ml beaker.

5. The solution is boiled and the lead oxide is added slowly tothe boiling solution with constant stirring.

6. It is filtered and again boiled.

7.The filterate thus obtained is added dropwise to this extract till precipitation occurs.

8.The filtrate is treated with animal charcoal to decolouriseextract.

9. The clear solution is extracted with 100mg of chloroform afterseparating by filtration.

10. The total solution is taken into distillation flask to remove thesolvent by distillation.

11. The residue left in the flask is dissolved in minimum amount of hot water and the dissolved contents are transferred to theboiling tube.

12. The solution is kept for slow crystallization.

13.  When the white crystalline solid comes out of the solution it isfiltered, dried in desiccators and weighed.

14. The above procedure is repeated for all samples of tea.

15. The observations are carefully recorded.

The chemistry involved in the experiment is as follows:

1. Caffeine being soluble in water goes into the solution on refluxing.

2. Lead oxide when added to lead acetatesolution helps lead to precipitate and comeout in the form of insoluble lead sulphate as it is a basic oxide.

3. The activated charcoal adsorbs the colouredpigments from the brown coloured solution. 

4. Chloroform is used for extracting the caffeineas it is a more soluble in CHCl3 than in coldwater.

5. On boiling caffeine being more volatileevaporates leaving a white mass behind.

6. On boiling caffeine being more volatileevaporates leaving a white mass behind.

OBSERVATION About 50 gm of each sample was taken. The contentsof caffeine of the samples were noted and theirpresence in terms of percentage was calculated.

NAME OF CAFFEINE PERCENTAGE TASTE THE TEA CONTENTS COMPOSITION

1. RED 0.029 0.0725% MILD &

LABEL SOOTHING

2. TAJ 0.05 0.0125% SLIGHTLY

MAHAL PLEASANT

3 TATA 0.036 0.09% STRONG

TEA PLEASANT

4 LIPTON 0.047 0.1175% VERY STRONG

INFERENCE 

FROM THE CAFFEINE CONTENT AND THE TASTEOF THE TEA AS DESCRIBED ABOVE SHOWS THAT THE GREATER THE AMOUNT OF CAFFEINE, THE BITTERNESS AND STIMULATING EFFECT OF THE TEA.