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The absorption of nitric oxide (NO) into aqueous solutions of ferrous chelates of nitrilotriacetic acid (NTA), ethylene diaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), and diethylenetriaminepentaacetic acid (DTPA) was studied in a stirred cell reactor. Experimental conditions were as follows: 0.05 less than or equal to CF(IIL) less than or equal to 0.1 kmol/mg(3), 8 less than or equal to P-NO less than or equal to 30 kPa, 3 less than or equal to pH less than or equal to 10 (NTA), or 7 less than or equal to pH less than or equal to 8 (EDTA, HEDTA, DTPA), C-L less than or equal to C-Fe(II) less than or equal to 3C(L) (NTA) or C-L = C-Fe(II) (EDTA, HEDTA, DTPA), and 293 less than or equal to T less than or equal to 333 K (NTA, EDTA, HEDTA) or T = 294 K (DTPA). The absorption leads to stable ferrous NO chelates. Due to the high reaction rate, in combination with the relatively high P-NO applied, the absorption rate is strongly affected by mass transfer limitation only. By applying penetration theory, the ratio of the diffusion coefficients of ferrous chelates and NO was determined: at T = 294 K (D(Fe(II)chelate)/D-NO)(1/2) = 0.44 +/- 0.01, 0.34 +/- 0.01, 0.36 +/- 0.01, and 0.31 +/- 0.015, for the ferrous NTA, HEDTA, EDTA, and DTPA complexes, respectively. At elevated T, (D(Fe(II)chelate)/D-NO)(1/2) decreases due to the unusual T-dt pendency of D-NO. For ferrous NTA, the formation of the ferrous NO chelate is;accompanied by pH effects that can be understood from iron chelate chemistry. In the case of ferrous NTA, pH