Picric acid or Trinitrophenol is, by far, one of the more dangerous chemicals being used today. Classified as a flammable solid when wetted with more than 30% water (UN1344, class 4.1) and a class A high explosive with less than 30% water (UN0154, class 1.1D), it has some very interesting properties. It is explosive but also highly shock, heat and friction sensitive. In fact, detonation with a speed and power superior to that of TNTcan occur by a 2 kg weight falling onto solid picric acid from a height of 36 cm. Picric acid is toxic by all routes of entry, it’s also a skin irritant and allergen and will produce toxic pro-ducts on decomposition.
Picric acid is used primarily in the manufacture of explosives and as an intermediate in dye manufacturing. It is also present in many laboratories, for use as a chemical reagent. Water is added to picric acid to act as a desensitizer. The wetted product is significantly less shock sensitive than the dry acid. Picric acid is highly reactive with a wide variety of chemicals and extremely susceptible to the formation of picrate salts. Many of these salts are even more reactive and shock sensitive than the acid itself.
Materials:
250 aspirin tablets each containing 325 mg acetylsalicylic acid
440 ml 98% sulphuric acid (drain cleaner)
153g potassium nitrate
1L isopropyl alcohol
Procedure:
1) Powder 250 aspiring tablets and place the powder in a beaker.
2) In another beaker, gently warm 1L of isopropyl alcohol and add it to the beaker containing the powdered aspirin.
3) Stir for 10 minutes then filter out and discard any solids collected.
4) Pour the filtrate into a shallow ceramic dish and heat in a simmering water bath until all of the isopropyl alcohol has evaporated and only acetylsalicylic acid remains.
5) Place the ceramic dish containing the acetylsalicylic acid in an oven set at 65 degrees Celsius for about 45 minutes to dry off any remaining moisture.
6) In another beaker, add the acetylsalicylic acid to 440 ml of 98% sulphuric acid stir for 5 minutes.
7) Heat the beaker to 70 degrees Celsius and hold it there while stirring until all of the acetylsalicylic acid has dissolved.
8) While vigorously stirring, slowly add 153g of potassium nitrate to the sulphuric acid/acetylsalicylic acid solution. The addition should take about 1 hour and 20 minutes.
9) Let the solution cool to room temperature then cool it to 5 degrees Celsius in an ice bath.
10) In another beaker, add 1kg of crushed ice to 400 ml cold water,
11) While stirring the ice/water, slowly add the contents of the beaker. This should precipitate out the picric acid.
12) Stir for 5 minutes and then let it sit for 15 minutes to let the precipitate settle at the bottom of the beaker.
13) Carefully pour off about 1L of the liquid and add 500 ml of cold water.
14) Filter out the picric acid and discard the filtrate.
15) In a beaker add the picric acid to 300ml of boiling water and stir. Add more water if all of the picric acid doesn’t dissolve.
16) Let the beaker cool to room temperature then cool it to 5 degrees Celsius in an ice bath.
17) Filter out the precipitate and discard the filtrate.