Informational purposes only! Do not attempt.
2,4,6-Trinitrophenol, more commonly known as picric acid is a powerful secondary explosive that finds uses as a booster and is also used in the synthesis of several other energetic compounds. TNP is useful in boosters because it can be initiated with ease by small amounts of a primary and is more powerful than TNT. TNP can be made from phenol, benzene, salicylic acid and acetylsalicylic acid but the acetylsalicylic acid nitration is most popular among hobby chemists because of acetylsalicylic acid's availability as aspirin tablets. Picric acid is very reactive and must be kept separate from metals, metal salts and bases so that it doesn't form sensitive picrate salts.
- Nitric acid is corrosive and toxic. MSDS
- Sulphuric acid is corrosive and toxic. MSDS
- Picric acid is corrosive, toxic, and explosive. Can cause kidney and liver damage. MSDS
- Nitrogen dioxide is corrosive and toxic in very small concentrations. Cause severe, irreparable damage to lungs from even low concentration exposures. MSDS
The quote below was in the SM thread on picric acid. Some food for thought.
- Potassium/sodium nitrate is an oxidizer. MSDS MSDS
- Acetylsalicylic acid MSDS
- Neoprene gloves.
- Splash goggles and/or faceshield.
- Fume hood or outside in very well ventilated area.
- Bucket of water to dump reaction vessel into in case of runaway.
Preparation of Trinitrophenol
- 10g Acetylsalicylic acid
- 60mL Concentrated sulfuric acid
- 20g Sodium nitrate or potassium nitrate
- Hot plate
- Stirring rod/magnetic stirrer
- Graduated cylinder
- 600mL Beakers
- Distilled water
- Crushed ice
- Filter paper/coffee filters
- 60mL concentrated sulfuric acid is measured in a graduated cylinder and added to a beaker is placed on a hot water bath and heated to 100C.
- Once the sulfuric acid is heated, 10g acetylsalicylic acid is added to the beaker and lightly stirred until dissolved. The solution turns dark brown to black as the acetylsalicylic acid is sulfonated to phenol-4-sulfonic acid. The solution is allowed to cool to 70C.
- Once cooled, 20g sodium nitrate is SLOWLY added to the phenol-4-sulfonic acid solution. The solution will foam and start to turn red as the sodium nitrate is added. The temperature of the reaction vessel is kept between 70C and 90C during the addition. If the nitrate addition is done too quickly, the toxic gas nitrogen dioxide will form. The addition took around 1 hour.
- After all sodium nitrate is added, the solution is heated to 100C in a hot water bath for 20 minutes. The solution turns from red to brown as the nitration finishes.
- The solution is cooled to 5C in an ice bath. A yellow-brown crust forming as the solution cools is normal.
- The reaction vessel is poured (or scooped, depending on how much crust formed) into a beaker containing 200mL ice water/crushed ice that is in an ice bath. More nitrogen dioxide at this step is a possibility. The yellow TNP crystals will precipitate. The beaker is decanted and more ice water is added. The solution is filtered and the collected TNP is dried. TNP will not dry if there is high sulfuric acid contamination and must be purified. Picric acid is shock, heat, and friction sensitive!
- Purification is achieved by dissolving the yield in 100mL boiling water and discarding the brown oily drops that rise to the top. The solution is then chilled and filtered.
TNP must not be stored in metal containers. It should be stored under a layer of water in glass or plastic containers with a stopper. Screw on caps should never be used because of the possibility of trace amounts in the threads of the cap being set off by friction. Picric acid should be kept away from light.
Picric acid should not be stored for long periods of time. During long storage times it has potential to form dangerously sensitive crystals.
As if kidney and liver damage weren't enough of a reason to avoid direct contact with picric acid, contact with skin will turn the affected area bright yellow for at least a week. Picric acid will stain just about everything it touches yellow.