The basic principle of preparing a small amount of nitrogen in the laboratory is to oxidize ammonia or ammonium salt with an appropriate oxidizer. The most commonly used methods are as follows: (1) Heating the solution of ammonium nitrite: (343k) NH4NO2 ===== N2↑+ 2H2O nitrogen machine (2) Sodium nitrite interacts with the saturated solution of ammonium chloride: NH4Cl + NaNO2 === NaCl + 2 H2O + N2↑ (3) Passing ammonia through red hot copper oxide: 2 NH3+ 3 CuO === 3 Cu + 3 H2O + N2↑ (4) Ammonia reacts with bromine water: 8 NH3 + 3 Br2 (aq) === 6 NH4Br + N2↑ 5 Ammonium bichromate heating decomposition: (NH4)2Cr2O7===N2↑+Cr2O3+4H2O {6} Heating sodium azide, so that its thermal decomposition, can get very pure nitrogen.