Tannin from tea

We have already allocated caffeine from tea. It turns out that tea can also provide tannin. It is a mixture of substances that are used for tanning leather, etching tissues before dyeing, in medicine - as an astringent; remember the astringent taste of strong tea. Tannin from tea can be obtained in the school chemical laboratory, but for industrial purposes there are other, inedible sources of tannin - ink nuts, sumac, etc.

Tannin from tea can be obtained in the school chemical laboratory

Further experiments with tea are best done in a chemical mug, observing the rules for handling chemicals: they require good skills, and substances that homes usually do not have. First, let's try to extract tanid from tea, and from them you can already get tannin.

For your experiments, take green tea, from which try to extract the tannin. In the absence of green tea, you can take and black tea, but it has much less tanid.

A small packet of green tea (50 g), pour in a saucepan half a glass (100 g) of boiling water and boil on low heat for about an hour to extract the solutes as completely as possible. The solution is filtered through several layers of gauze or through a cotton cloth folded in half; wash the filter cake with hot water (half a cup). You will receive about a glass of yellow-green solution.

Pour 15-20 g of lead acetate into the liquid or a suitable amount of lead lotion. Keep in mind that lead acetate should not enter your mouth: it can cause poisoning. Gently drain the liquid, add a glass of hot water to the precipitate, stir, let stand and drain again. Repeat this operation 3-4 times to remove the lead ions. Check if they are really removed by taking a sample of the liquid and adding to it in the test tube a few drops of dilute sulfuric acid. If lead remains, the solution will become cloudy; In this case it is necessary to repeat washing. When the sample is negative, filter out the sediment (this is lead tannate) through glass wool and on the filter, rinse 50 ml of approximately 1% sulfuric acid solution. After collecting the solution, neutralize the acid by adding a 0.5% solution of barium hydroxide dropwise, and then filter out the precipitated barium sulphate precipitate.

The remaining clear solution contains tannin from tea. Reduce it to dryness in a water bath. The remaining tannin on the bottom is scraped and pulverized.

Here are a few beautiful reactions with tannin.

Approximately 0,5 g of tannin is dissolved in 40 ml of water. Once you add a solution of iron (III) chloride or another ferric salt, the liquid will immediately blacken. This - the ancient ink, only the tannin for them was extracted from oak (ink) nuts, outgrowths on leaves and young shoots of oak.

Another bright experience: about 0.3 g of tannin is placed in a small tube and drip three drops of concentrated hydrochloric acid. Forms flobbafen - a substance of red color.

Next, add a little tannin to a solution of silver nitrate AgNO3 (lapis); Suits and a pencil from the pharmacy. This time will precipitate a silver tannate precipitate. It has a brown color.

And the last experience with tannin. In a 2% solution of hydrochloric acid, dissolve about 0,3 g of vanillin (or the corresponding amount of vanilla sugar) and add three times less tannin. Appear raspberry staining. This is a characteristic reaction for tannin.