styphnic acid

     Styphnic acid, also called 2,4,6-trinitroresorcinol, is a yellow crystalline primary explosive similar to picric acid. Other names for the compound include 2,4,6-trinitro-1,3-benzenediol; 2,4-dihydroxy-1,3,5-trinitrobenzene; resorcinic acid; trinitroresorcin; trinitroresorzin; oxypicric acid; styphninsaure; TNR; and StA. Industrially it is used as an explosive and as a dye. It first listed preparation was published by Mertz and Zetter in 1879. Styphnic acid forms many explosive salts, the preparation of which are included here. The higher cost of styphnic acid vs. picric acid means it is less often used. The lead salt is the most commercially utilized form. Styphnic acid and its salts are most often used in detonators either alone or in mixtures.

CHEMICALS	APPARATUS
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     Synthesis 1: Into a large beaker very slowly add 100 parts of resorcinol, with stirring, to 1000 parts of 93-98% sulfuric acid over a period of 30 minutes. Regulate the rate of addition to keep the temperature around 50 C, and maintain that temperature for 15 minutes after the addition is complete. Add to this still hot mixture 110 parts of 90% nitric acid, with rapid stirring, over a period of 30-50 minutes while maintaining the temperature between 50 and 55 C. Add a second portion of 90 parts of nitric acid at a slower rate (1.5-2 hours) and with reduced stirring while maintaining the temperature between 55 and 60 C. If styphnic acid begins to crystallize while the second portion of acid is being added increase the rate of acid addition while providing cooling for the beaker to maintain the temperature at 60-65 C. Continue stirring for an additional 30 minutes after all of the acid has been added while maintaining the temperature between 60 and 65 C. Allow the reaction mixture to cool to room temperature and then carefully decant off as much acid as possible. Drown the remaining crystals of styphnic acid with ice cold water and pour over a filter to collect the crystals. Thoroughly wash the crystals of styphnic acid with ice cold water to remove all traces of acid and dry at 60 C. There is the possibility the reaction will cause excessive foaming. To avoid this try to stay within the temperature rages as close as possible, and avoid vigorous stirring when the second portion of nitric acid is added. Synthesis 2: Prepare a solution of 15.42 g of resorcinol in 400 mL of water with 80 g of crushed ice in a 1-L beaker. Immerse the beaker into a salt-ice bath to chill the contents and slowly add 16 mL of concentrated (>95%) sulfuric acid. Prepare a second solution of 20.52 g of sodium nitrite in 150 mL of water, and cool this solution to 0 C. Slowly add, with stirring, the nitrite solution to the resorcinol solution over a period of 45 minutes while maintaining the temperature at 0-4 C. Allow the reaction to proceed an additional 3 hours while keeping it at 0 C. Crystals of crude 2,4-dinitroresorcinol should form. Filter the crystals to collect them and allow to dry for 10-12 hours. CAUTION: this next procedure generates large amounts of toxic nitrogen dioxide gas, use adequate ventilation! Place 65 mL of concentrated (>98%) nitric acid in a 500-mL beaker and cool it in a salt-ice bath to 0 C. Slowly add small portions of dinitroresorcinol, with stirring, to the acid over a period of 70 minutes while maintaining the temperature between 4 and 8 C. After the addition is complete remove the beaker from the ice bath and allow the mixture to warm up to room temperature. It is then slowly heated to 75 C over a period of 2 hours with continuous stirring and held at 75 C for 45 minutes while the reaction completes. Allow the mixture to cool to room temperature, and then drown it with ice cold water to dilute the acid. Quickly pour the mass over a filter to collect the crystals of styphnic acid. The product is washed with five 40 mL portions of ice cold water and dried in vacuum. Yield is about 28 g or 84%. Synthesis 3: Prepare a solution of 5.5 g of resorcinol and 2.4 g of sodium hydroxide in 100 mL of water in a 250-mL beaker. Place the beaker in a salt-ice bath and cool the contents to under 0 C. With vigorous stirring slowly add 7 g of sodium nitrite to the solution, and then slowly add 10 mL of 44% sulfuric acid along with some ice to prevent a rapid temperature rise. Add an additional 44 mL of 44% sulfuric acid over a period of 90 minutes while keeping the temperature as close to 0 C as possible. Continue stirring for 1 hour after all of the acid has been added. The solution will turn a pale brown and yellow crystals should begin to separate. Pour the solution over a filter to collect the crystals and wash them with ice cold water to remove any trace of acid. Recrystallize the compound in dilute ethyl alcohol to give a pure sample of 2,4-dinitroresorcinol as a yellow brown powder. CAUTION: this next procedure generates large amounts of toxic nitrogen dioxide gas, use adequate ventilation! Prepare a solution of 700 g of 65% nitric acid in 300 mL of water and a second solution of 100 g of 2,4-dinitroresorcinol in 600 mL of water cooled to 0 C (the dinitroresorcinol need not be completely dissolved). Slowly add, with stirring, the nitric acid solution to the dinitroresorcinol solution. Heat the combined solution on a water bath until the vigorous reaction and evolution of red fumes ceases and the solution is clear. Allow the solution to cool to room temperature; yellow crystals should precipitate. Filter to collect the crystals and recrystallize them from benzene to obtain pure pale yellow styphnic acid. Yield is around 120 g or 81%. Styphnic acid may be safely stored by wetting with a small quantity of dilute sodium carbonate solution. Magnesium styphnate This compound is a soluble salt of styphnic acid. It is most often used to make the other styphnate salts through displacement reactions. Magnesium styphnate can be prepared by dissolving 1 part of styphnic acid in 25 parts of water and heating to 80 C. Add 1 or more parts (an excess) of magnesium oxide, hydroxide, or carbonate to the solution with stirring. Filter to remove any unreacted magnesium oxide and gently heat the filtrate to drive off the water until moist crystals of magnesium styphnate are obtained (do not distill to dryness). Place the crystals in a desiccator, vacuum preferably, to remove the final traces of water. If the magnesium styphnate is being used to prepare other salts, the lead salt for example, there is no need to isolate the crystals; just use the aqueous solution. The following procedure can be used to prepare large quantities of magnesium styphnate, or scaled down accordingly: Prepare a solution of 27.5 Kg of styphnic acid in 70 L of water. Heat the solution to 45 C and add 11.3 Kg of magnesium carbonate in small portions with stiring. Allow the solution to cool to room temperature, and then filter to remove any impurities or unreacted carbonate. This solution can be used to make a large quantity of lead styphnate as described in its page. Silver styphnate This compound is used as an alternative to lead styphnate in primer compounds. It is reported as being superior in performance and stability to lead styphnate, less toxic, but more expensive. It may be prepared by mixing a solution of styphnic acid in ethyl alcohol and adding a small quantity of sodium carbonate. The solution is then acidified with glacial acetic acid and brought to a boil. Add a small quantity of aqueous silver nitrate with stirring to complete the reaction. Allow the solution to cool to room temperature; crystals of silver styphnate should have precipitated. Filter to collect the crystals, wash them with water to remove soluble impurities, and allow to dry. Barium styphnate This compound is an explosive styphnate salt used in primer and delay compositions either in mixtures or by itself. Its explosive properties are inferior to that of lead styphnate. It may be prepared by mixing a solution of 37.3 g of magnesium styphnate in 213 mL of water. Prepare a second solution of 35.7 g of barium acetate monohydrate in 196 mL of water. Heat the barium solution to 75 C and slowly add, with stirring, the styphnate solution to the barium solution over a period of 20 minutes while maintaining the temperature at 75 C. Continue stirring for 1 minute, and then add 23.7 mL of 15.2% nitric acid over a period of 10 minutes while maintaining the temperature at 75 C. Continue stirring for an additional 15 minutes, and then allow the solution to cool to room temperature. Decant off as much of the liquid as possible before filtering to collect the precipitate of barium styphnate. Wash the crystals thoroughly with water and dry in an oven at 45 C. Another preparation of barium styphnate with uniform free flowing crystals is as follows: Prepare a solution of 345.6 mL of 0.85% sodium carboxymethyl cellulose and add to it a solution of 215.4 g of magnesium styphnate in 800 mL of water. Prepare a third solution of 194.5 g of barium chloride dehydrate in 800 mL of water; heat this solution to 85 C. Slowly add, with stirring, the styphnate solution to the barium solution over a period of 20 minutes while maintaining the temperature at 85 C. Continue stirring for 15 minutes at this temperature after the addition is complete. The liquid is decanted while still hot, the precipitate of barium styphnate is filtered to collect it, the crystals are washed twice with water and once with alcohol, and they are dried at 40 C in an oven. Zinc styphnate Prepare a solution of 72 g of styphnic acid and 24 g of zinc oxide in 200 mL of water. Stir for several minutes to allow the reaction to go to completion, and then pour over a filter to remove any unreacted zinc oxide or impurities. Add 700 mL of water to the filtrate and then add enough dilute sodium hydroxide to bring the solution to a pH of 7. This solution can be used as is to make lead styphnate. Manganous styphnate Prepare a solution of 72 g of styphnic acid and 34 g of manganous carbonate in 200 mL of water. Stir for several minutes to allow the reaction to go to completion, and then pour over a filter to remove any unreacted manganous carbonate or impurities. Add 700 mL of water to the filtrate and then add enough dilute sodium hydroxide to bring the solution to a pH of 7. This solution can be used as is to make lead styphnate.

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