Introduction:
Picric acid has a detonation velocity of 7480 m/s and has a melting point of 123 degrees Celsius. It's quite toxic and is absorbed through skin. Breathing the dust of the dry powder is also dangerous. Respirator and gloves should be worn when handling this explosive. Picric acid will form dangerously sensitive picrate salts if it is exposed to metals.
Materials:
125 aspirin tablets containing 325mg acetylsalicylic acid
220ml 98% sulphuric acid
77g potassium nitrate
500ml 99% isopropyl alcohol
Heres a picture of the chemicals needed to prepare picric acid. From left to right there’s potassium nitrate, sulphuric acid, 99% isopropyl alcohol, and aspirin (acetylsalicylic acid)
Procedure:
The first thing we must do is purify the aspirin and remove any fillers or binders in the pills. After this step, you'll have pure acetylsalicylic acid. We do this with isopropyl alcohol. This process must be done in a place with very good ventilation. When purifying aspirin, you must evaporate large amounts of alcohol. This is safe if done outside, but can be very dangerous if done without proper ventilation. Powder 125 aspirin tablets each containing 325mg of acetylsalicylic acid. Pour the powdered aspirin in a beaker and set it aside. In another beaker, warm 500ml of 99% isopropyl alcohol to 60 degrees Celsius in a simmering water bath. When the temperature of the alcohol reaches 60 degrees, remove it from the heat source and add the powdered aspirin. Vigorously stir for 2 minutes then filter the liquid through 2 coffee filters and keep the filtrate. Discard the aspirin impurities left in the coffee filter. Pour the alcohol/aspirin solution into a shallow dish and gently heat it in a hot water bath until all of the alcohol has evaporated leaving pure acetylsalicylic acid. On the right is a picture taken after the aspirin was added to the alcohol.
In another beaker, add the acetylsalicylic acid to 220ml of 98% sulphuric acid and heat it to 70 degrees Celsius on a simmering water bath. Hold the temperature at 70 degrees and stir until all of the acetylsalicylic acid has dissolved. After adding the acetylsalicylic acid, the solution usually turns black. I would have taken a pic of this change in colour, but my sulphuric acid is black so there was no colour change. Once all of the acetylsalicylic acid has dissolved, remove the beaker from the heat source. While vigorously stirring, add 77g of potassium nitrate over a period of 1 hour. Add a little more than a gram per minute, while constantly stirring. During potassium nitrate addition, nitrogen dioxide is given off. Do this step outside or somewhere with very good ventilation. When potassium nitrate is added, the colour of the solution changes from black to red/orange then back to black. When most of the potassium nitrate has been added, the colour of the solution in usually very dark red, although not always. To the left is a picture of the solution after a small amount of potassium nitrate was added.
After the potassium nitrate addition, let the solution cool to room temperature then cool it to 5 degrees in an ice bath. Once the liquid has been cooled to 5 degrees, you should have a suspension thick with picric acid crystals. On the right is a picture of the picric acid suspension after being cooled. In another beaker, add 500g of ice to 200ml of water. While stirring the ice/water, slowly add the picric acid solution. Wait 15 minutes for the picric acid to settle at the bottom of the beaker, then pour off 500ml of the liquid and add another 250ml of water. Filter the liquid through 2 coffee filters and discard the filtrate. The yellow solid left in the coffee filter is picric acid. In another beaker, bring 200ml of water to a boil. When the water starts boiling, remove it from the heat source and add the picric acid and stir for 5 minutes. Cool the picric acid solution to 5 degrees by using an ice bath and then filter off the picric acid using 2 coffee filters. Now you have reasonably pure picric acid. "
PREPARATION OF PICRIC ACID FROM ASPIRIN Picric acid can be used as a booster explosive in detonators or as an intermediate to preparing lead picrate or DDNP. MATERIAL REQUIRED: - Aspirin, 20 tablets (5 grain/tablet) - Alcohol, 95% pure - Concentrated sulfuric acid (boil battery acid until white fumes appear) - Potassium nitrate (saltpeter) - Water - Canning jar (1 pint) - Hot water bath - Paper towels (for filter) - Glass tube or rod - Glass containers - Dish (ceramic or glass) - Heat source - Cup - Teaspoon PROCEDURE: 1. Crush 20 tablets of aspirin in a glass container and work into a paste with a teaspoon of water. 2. Add approximately 1/3 - 1/2 cup (100 ml) of alcohol with stirring and filter through a paper towel into another glass container. If aspirin is pure enough (usually cheap priced aspirin are) then Steps 1, 2 and 3 can be omitted and can proceed and add crushed aspirin to Sulfuric Acid. 3. Discard the solid left on the paper and pour the liquid from the container into the dish. Evaporate the alcohol and water on a hot water bath, leaving a white powder. 4. Add this white powder to 1/3 cup (80 ml) of concentrated sulfuric acid in a canning jar. 5. Heat the jar in a simmering hot water bath for 15 minutes and remove. Stir; solution will gradually turn black. 6. Add 3 level teaspoons (15 gm) of potassium nitrate in three portions with vigorous stirring. After heating put jar in cold water and add potassium nitrate. 7. Allow the yellow-orange solution to cool to room temperature with intermittent stirring. Solution is darker than yellow-orange. 8. Pour the solution into 1-1/4 cups (300 ml) of water (cold if possible) and allow to cool. Upon pouring, solution is now yellow-orange. 9. Filter the mixture through a paper towel and wash the light yellow material (picric acid) with 1/8 cup (25 ml) of water through paper towel. Takes considerable time to filter if genuine filter paper is used. 10. Dry at 160-200 degrees F for two hours. The yield is 4.0-4.5 grams.
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ALTERNATIVE SYNTHESIS: Picric Acid can also be produced from Phenol derivatives such as Salicylic and Acetylsalicylic acids. The procedure is exactly the same as the one outlined above, except a smaller amount of Salicyclic (0,6grams per 1mL H2SO4 and 1,5mL HNO3) our Acetylsalicylic (0,5g per 1mL H2SO4 and 1,5mL HNO3) acids are used. This is important because Acetylsalicylic acid is the active ingredient in aspirin and can be obtained by dissolving them in hot ethanol (20 500mG pills per 100mL), filtering out the buffers, and allowing the pure acid to crystallize out. The reaction than goes: H2SO4 C9H8O4 -------> C2H4O2 + C7H4O2 (The sulfuric acid breaks down the acetylsalicylic acid to acetic and salicylic acid) Or if Salicylic acid is used, C7H4O2 + H2O ---> C6H6O + CO2 (Salicylic acid with heat source converts to carbolic acid (phenol) and carbon dioxide; (in presence of water from 98% H2SO4) Or the formed phenol just sulfonates rapidly. From Phenol-4-sulfonic acid onwards the reaction proceeds as outlined above. The Nitric Acid can also be substituted by adding 15 grams Sodium Nitrate per 80mL H2SO4. With the NaNO3/H2SO4 nitrating system (H2SO4 already present) without any external cooling; the phenolsulfonic acid compound readily nitrates to a polynitro compound (2,4,6-trinitrophenol). Yet another way of preparing picric acid is by the conversion of benzene directly into picric acid in one step. This was patented by Mueller Teeters in 1948 (US pat. 2,455,322): 1g of mercuric nitrate is added to 60mL of 70% nitric acid which is than stirred and added to 23 mL of benzene. The mixture is than heated for several hours and distilled. Benzene will distill over first, then nitrobenzene, and finally a mixture of dinitrobenzene and dinitrophenol will come over slowly. The distillation is continued until these volatile organics are removed. The remaining residue is filtered while hot to remove any impurities and allowed to crystallize. the picric acid that should have crystallized can be purified by recrystallizing from hot water. Picric Acid can be used alone or in the synthesis of picrate salts such as, for example:ALTERNATIVE SYNTHESIS:
Picric Acid can also be produced from Phenol derivatives such as Salicylic and Acetylsalicylic acids. The procedure is exactly the same as the one outlined above, except a smaller amount of Salicyclic (0,6grams per 1mL H2SO4 and 1,5mL HNO3) our Acetylsalicylic (0,5g per 1mL H2SO4 and 1,5mL HNO3) acids are used. This is important because Acetylsalicylic acid is the active ingredient in aspirin and can be obtained by dissolving them in hot ethanol (20 500mG pills per 100mL), filtering out the buffers, and allowing the pure acid to crystallize out. The reaction than goes:
H2SO4
C9H8O4 -------> C2H4O2 + C7H4O2
(The sulfuric acid breaks down the acetylsalicylic acid to acetic and salicylic acid)
Or if Salicylic acid is used,
C7H4O2 + H2O ---> C6H6O + CO2
(Salicylic acid with heat source converts to carbolic acid (phenol) and carbon dioxide; (in presence of water from 98% H2SO4)
Or the formed phenol just sulfonates rapidly. From Phenol-4-sulfonic acid onwards the reaction proceeds as outlined above.
The Nitric Acid can also be substituted by adding 15 grams Sodium Nitrate per 80mL H2SO4.
With the NaNO3/H2SO4 nitrating system (H2SO4 already present) without any external cooling; the phenolsulfonic acid
compound readily nitrates to a polynitro compound (2,4,6-trinitrophenol).
Yet another way of preparing picric acid is by the conversion of benzene directly into picric acid in one step. This was patented by Mueller Teeters in 1948 (US pat. 2,455,322): 1g of mercuric nitrate is added to 60mL of 70% nitric acid which is than stirred and added to 23 mL of benzene. The mixture is than heated for several hours and distilled. Benzene will distill over first, then nitrobenzene, and finally a mixture of dinitrobenzene and dinitrophenol will come over slowly. The distillation is continued until these volatile organics are removed. The remaining residue is filtered while hot to remove any impurities and allowed to crystallize. the picric acid that should have crystallized can be purified by recrystallizing from hot water.
Picric Acid can be used alone or in the synthesis of picrate salts such as, for example:
