In this article we will discuss about the tests for detection of tannins in plants.

Tannins are a heterogeneous group of organic compounds found in plants. They are commonly present in unripe fruits — guava, banana and leaves of tea etc. These are water-soluble compounds. The metabolic significance of these compounds are not clearly known but they play a significant role in disease resis­tance in certain plants.

Requirements for Detection of Tannins:

(a) Preparation of Sample Solution:

Tannins can be easily extracted by boiling the plant materials in water.

The extract is filtered and following tests are performed:

(b) Reagents:

1. Ferric chloride (5%) solution.

2. Dilute NH4OH solution.

3. Potassium ferricyanide solution (5%).

4. Iodine solution (1%).

5. Dilute HNO3 solution.

6. Acetic acid.

7. Potassium dichromate solution (5%).

8. Silver nitrate solution (10%).

Tests for Detection of Tannins:

Experiment:

Test 1:

A few drops of 5% Ferric Chloride solution is added to the extract of tannin.

Test 2:

To a small quantity of extract dilute NH4OH is added, followed by addition of potassium ferricyanide solution.

Test 3:

A few drops of Iodine solution are added to the tannin extract

Test 4:

A few drops of dilute HN03 are added to the tannin extract to the tannin extract.

Test 5:

A few drops of acetic acid are added to the extract.

Test 6:

A few drops of Potassium dichromate are added to the extract.

Test 7:

In a test tube, tannin extract is taken and to it a drop of dil. NH4OH is added. Then excess of 10% AgNO3 soln. is then excess of 10% AgNO3 soln. is added. The mixture is placed in a added. The mixture is placed in a

Observation:

A deep blue-black colour is formed

The solution turns red in colour

A transited red colour is formed

The solution turns dark red in colour

The solution produces red ppt.

Initially a white precipitate is formed. Then a dark silver mirror is formed on the wall of the test tube.

Inference:

Presence of Tanni.

Presence of Tanni.

Presence of Tanni.

Presence of Tanni.

Presence of Tanni.

Presence of Tanni.

Presence of Tanni.

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