Tuesday, 3 June 2014

Basic techniques that we learnt in this experiment -3B

At first we were given 8 teabags and tea leaves.
In the tea leaves,there are 3 chemicals.They are cellulose,caffeine and tannins.
(The cellulose is not soluble and tannins are bitter in taste.)
Our challenge was to extract caffeine from the mixture consisted of caffeine and tannins.
So in order to achieve this,we had to put calcium carbonate powder to keep the tannin joining the caffeine.

When we extracted caffeine  by distilling off the dichloromethane on a rotary evaporator,we had to use hot water.This is because as the temperature increases,the effects will also increase.

During the 'Buchner' filtration,we had to use 2 filter papers to purify the suspension.Then we had to apply pressure by turning the 'pressure button' in anti-cockwise way.
After that,the bubbles could be seen in the purified filtrate.

Next we had to put the flask inside the basin of cold water in order to cool the filtrate down to the room temperature.

When we used separating funnel,we could see two layers.The top layer was aqueous layer and the bottom layer was organic layer. The different density caused different layers.The organic layer was at the bottom because it had a higher density.

Although we had gone through filtration,the organic layers were not pure.So we had to add magnesium sulphate powder.The magnesium sulphate powder clumps in the presence of water.

During the process of extraction,the flask was cold  due to the evaporation of dichloromethane.

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