Abstract: Nitrous oxide having a high purity is produced by reacting urea, nitric acid and sulfuric acid at a temperature of 40.degree. through 100.degree. C., and isolating the resultant nitrous oxide from the reaction gas mixture, without any danger of, for example, explosion during the reaction and without using expensive catalysts and sulfamic acid.

Abstract: A process for removing nitrogen oxides (NO.sub.x) from a waste gas containing 300 through 20,000 ppm of NO.sub.x is disclosed. In the process, the waste gas containing NO.sub.x is adjusted to a molar ratio of NO/NO.sub.2 of approximately 1 and is then scrubbed with a scrubbing solution containing an alkali metal hydroxide in a first column. The scrubbing solution is removed from the first column before the alkali metal hydroxide is completely consumed. The removed scrubbing solution is then contacted in a second column with a gas having 1.0 through 60.0% by volume NO.sub.x which has been adjusted to a molar ratio of NO/NO.sub.2 of approximately 1. Thus, the NO.sub.x content of the purified gas can be lowered to far less than 200 ppm and post-treatment problems of the scrubbed solution can be effectively solved.