Prepare solution 20.8g sodium nitrite and 11g of copper sulphate (CuSO4*5H2O) in 60 ml of hot water, resulting solution contains copper nitrite and has dark green color. Prepare solution of 10.3g aminotetrazole (ATZ) and 0.4g CuSO4*5H2O in 12.8 ml 70% nitric acid + 120 ml of water. Diazotetrazole is intermediate in nitrotetrazole synthesis, it can explode in solution if concentration will reach 2% from the slightless stimulus, even at 0C. Microexplosions are not dangerous but acting on nerves. To completely avoid them, slow addition, effective stiring and carefull temperature control are essential. Small adition of copper sulphate to ATZ solution is essential to avoid microexplosions in drops, on contact with nitrogen oxides, escaping from reaction mixture. Copper nitrite solution is placed on ice bath and cooled to 5C, then solution of ATZ in nitric acid, is added slowly with stirring (perfectly drop by drop). During addition temperature of reaction mixture must be kept below 15C all times. If mixture begins to foam, addition is paused and mixture is well stirred until foam dissapears before next portions of ATZ solution are added (foaming is result of HNO2 decomposition to water and NOx if it's concentration is too high). Reaction is proceeding smoothly, without microexplosions, with small evolution of NOx, if conditions are carefully controlled. Whole addition process takes time about 1.5 hours. Close to end of addition mixture becomes thicker, and changes color to green- blue (similar with homemade CuCO3*Cu(OH)2). After addition is completed mixture is left to sit in ice bath for 15 minutes, after that 14 ml of 70% nitric acid + 6 ml of water is added with stirring. Reaction mixture is left for 1 hour, solid precipitate of acid copper salt of nitrotetrazole is filtered off, washed with 5.72 ml HNO3 + 44 ml H2O and with three portions of 50 ml H2O. Yield is about 85%. Product is bluish - green crystals, almost insoluble in cold water.

Warning!!! Acid copper salt of nitrotetrazole is powerfull and sensitive explosive. It is almost completely safe then wet, but in dry state it can explode violently on friction, impact or heating. Safety precautions must be remembered all times.

Below are the photos of process. Left photo shows solutions of copper nitrite (left one) and ATZ in nitric acid with CuSO4 added (right one). Photo in the middle shows ice bath with sitting reaction flask, and termocouple temperature control. Right photo shows reaction product on filter.

Acid copper salt of nitrotetrazole can be easily converted to soluble salts of nitrotetrazole by heating in solution of corresponding hydroxides. For example solution of sodium 5-nitrotetrazolate can be prepared by boiling acid copper salt in NaOH solution: Cu(NT)2*HNT + 3NaOH => 3NaNT + CuO+ 2H2O. Solid black copper oxide is removed by filtering, pure solution of NaNT can be concentrated to separate solid salt, or can be used dirrectly for further reactions.

Prepare solution 20.8g sodium nitrite and 11g of copper sulphate (CuSO4*5H2O) in 60 ml of hot water, resulting solution contains copper nitrite and has dark green color. Prepare solution of 10.3g aminotetrazole (ATZ) and 0.4g CuSO4*5H2O in 12.8 ml 70% nitric acid + 120 ml of water. Diazotetrazole is intermediate in nitrotetrazole synthesis, it can explode in solution if concentration will reach 2% from the slightless stimulus, even at 0C. Microexplosions are not dangerous but acting on nerves. To completely avoid them, slow addition, effective stiring and carefull temperature control are essential. Small adition of copper sulphate to ATZ solution is essential to avoid microexplosions in drops, on contact with nitrogen oxides, escaping from reaction mixture. Copper nitrite solution is placed on ice bath and cooled to 5C, then solution of ATZ in nitric acid, is added slowly with stirring (perfectly drop by drop). During addition temperature of reaction mixture must be kept below 15C all times. If mixture begins to foam, addition is paused and mixture is well stirred until foam dissapears before next portions of ATZ solution are added (foaming is result of HNO2 decomposition to water and NOx if it's concentration is too high). Reaction is proceeding smoothly, without microexplosions, with small evolution of NOx, if conditions are carefully controlled. Whole addition process takes time about 1.5 hours. Close to end of addition mixture becomes thicker, and changes color to green- blue (similar with homemade CuCO3*Cu(OH)2). After addition is completed mixture is left to sit in ice bath for 15 minutes, after that 14 ml of 70% nitric acid + 6 ml of water is added with stirring. Reaction mixture is left for 1 hour, solid precipitate of acid copper salt of nitrotetrazole is filtered off, washed with 5.72 ml HNO3 + 44 ml H2O and with three portions of 50 ml H2O. Yield is about 85%. Product is bluish - green crystals, almost insoluble in cold water.

Warning!!! Acid copper salt of nitrotetrazole is powerfull and sensitive explosive. It is almost completely safe then wet, but in dry state it can explode violently on friction, impact or heating. Safety precautions must be remembered all times.

Below are the photos of process. Left photo shows solutions of copper nitrite (left one) and ATZ in nitric acid with CuSO4 added (right one). Photo in the middle shows ice bath with sitting reaction flask, and termocouple temperature control. Right photo shows reaction product on filter.

Acid copper salt of nitrotetrazole can be easily converted to soluble salts of nitrotetrazole by heating in solution of corresponding hydroxides. For example solution of sodium 5-nitrotetrazolate can be prepared by boiling acid copper salt in NaOH solution: Cu(NT)2*HNT + 3NaOH => 3NaNT + CuO+ 2H2O. Solid black copper oxide is removed by filtering, pure solution of NaNT can be concentrated to separate solid salt, or can be used dirrectly for further reactions.