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The interaction of urea and nitrogen oxides produces N 2. This reaction is used in neutralization of nitrogencontaining technological gases and wastes of power, metallurgic, and metal working plants. 1 It is generally accepted 2-4 that urea reacts with nitrous acid according to the equation CO(NH2) 2 + 2 HNO 2 9 2 N 2 + CO 2 +3 H20.However, in acidic solutions urea may also undergo hydrolysis producing CO: and NH4 + ions. 4 Available data on the product composition and kinetics of urea reactions with nitrogen oxides and nitrous acid are insufficient for complete description of occurring processes.We investigated in detail the interaction of HNO 2 with urea in aqueous solutions of HNO3 containing 0.05--0.2 M CO(NH2) 2 and NaNO2 and 0.02--1.0 M HNO 3 with magnetic stirring. Time variation of the solution contents was monitored by titrimetry (determination of H +, HNO 2 and CO(NH2)2) and ionometry . .with use .of.ion-selective electrodes _(NH4~" .andNO.if).Gaseous products were identified by IR spectroscopy and with the use of a ~I'esto-3Y' automatic gas analyzer. We found that the reaction between CO(NH2)2 and HNO 2 within a temperature range of 10--50 ~ follows the stoichiometric equation CO(NH2) 2 + HNO 2 + H + ,, 9 N 2 + NH4 + + CO 2 + H20.The reaction orders with respect to CO(NH2)2 and HNO 2 are equal to unity. The effective reaction rate constant keff grows proportionally to the H * ion concentration within the range from 0.01 L tool -t s -I when [H +] = 0.02 tool L -I to 0.30 L mo1-1 s -1 when [H +] = 1.0 mol L -1 (25.0+_0.1 ~ In our opinion, the essential determining factor in the H + concentration range under study is the fraction of the protonated form of CO(NH2) 2. Assuming that the reaction involves H2NCONH3 +, we calculated the rate constant /c o independent of the H + ion concentration with the use of the dissociation constant of the urea protonated formS:The concentration of the urea protonated form is determined by the expression K+[H +1

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