Caution: Both phenol and picric acid are very poisonous
and can penetrate the skin! – Avoid any contact!

1) Synthesis of Picric Acid

Use a fume chamber! – Toxic gases will be evaporated during reaction!

Weigh 1 [g] of phenol into an ordinary test-tube and dissolve it with one drop of water. Fill 10 [ml] of conc. nitric acid into a hardly-fusible test-tube of medium size.
Add the phenolic solution in 5 portions to the acidic solution. Vigorous reaction! – After a short break continue by warming carefully the test-tube. As soon as brown fumes occur interrupt the heating! - When the colour of the solution turns from brown to red the reaction is complete.
Allow to cool and you´ll obtain a precipitate of picric acid. Dilute with water and filter. For purification a recrystallization is used. Fill the picric acid into a small test-tube and fill it to 1/3 with hot water. After cooling impurities are dissolved in the water and after further filtration you´ll yield picric acid.


2) Picric Acid as a Dye

Prepare in a 250-ml-beaker a very diluted solution of picric acid. Add some woolen fibres (or silk) and boil for a few minutes.
Remove the fibres and wash them with water until the washing liquid is colourless.
Now heat some of the fibres with 1% ammonia solution.

Observation?


3) Reaction with glucose

Prepare in a test-tube ca. 2 [ml] of a saturated solution of picric acid. Add 1 [ml] of a solution of sodium carbonate and another 1 [ml] of glucose solution.
Warm the mixture.

Observation?

This reaction is used to determine the concentration of glucose in our blood!


Additional task: Read in Wikipedia about the uses of picric acid!