Chemical test performed to detect (i) vanaspati in butter, (ii) Argemone oil in groundnut oil and (iii) Metanil yellow in pulses are stated as follows:
To detect the presence of vanaspati in butter:
We will take a teaspoonful of butter sample to be tested in a test-tube and melt it by warming the test-tube. An equal amount of conc. Hydrochloric acid (HCI) and a pinch of common sugar is then added. Shake the test tube for about one minute to mix and then keep it aside for five minutes. After five minutes, observe the color of the lower layer. Appearance of a deep red color (crimson color) in the lower layer shows the presence of vanaspati in butter.
To detect the presence of argemone oil in groundnut oil:
We take the groundnut oil sample in a test tube and add some concentrated nitric acid (HNO3) to it. Shake the test tube carefully and observe the color of the acid layer. Appearance of a red or reddish-brown color in the acid layer shows the presence of argemone oil in the groundnut oil.
To detect metanil yellow in pulses:
We take about 5 grams of pulses in a test tube and then add about 5 millilitre of water. Shake the test tube well. Then add a few drops of conc. hydrochloric acid (HCI) to the test tube. Appearance of a pink color in the solution shows the presence of metanil yellow in pulses.