Carbon dioxide equivalent of "emissions" or rate of greenhouse gas emission—a "flow" into the atmosphere—rather than the instantaneous value of the radiative forcing of the "stock" (concentration) of greenhouse gases "in the atmosphere" described by e. The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the GWP of the gas. The following units are commonly used: For example, the GWP for methane over 100 years is 34 and for nitrous oxide 298. This means that emissions of 1 million metric tonnes of methane and nitrous oxide respectively is equivalent to emissions of 34 and 298 million metric tonnes
Nitrous oxide careful heating of ammonium nitrate at about 250 C, which decomposes into nitrous oxide and water vapour. The addition of various phosphate salts favours formation of a purer gas at slightly lower temperatures. This reaction may be difficult to control, resulting in detonation. The decomposition of ammonium nitrate is also a common laboratory method for preparing the gas. Equivalently, it can be obtained by heating a mixture of sodium nitrate and ammonium sulfate: Another method involves the reaction of urea, nitric acid, and sulfuric acid: Direct oxidation of ammonia with a manganese dioxide-bismuth oxide catalyst has been reported: cf. Ostwald