A recent report on an intense CO2 and CO evolution in the Briggs-Rauscher (BR) reaction revealed that iodination of malonic acid (MA) is not the only important organic reaction in the classical BR oscillator. To disclose the Source of the gas evolution. iodomalonic (IMA) and diiodomalonic (I(2)MA) acids were prepared by iodinating MA with nascent iodine in it semibatch reactor. The nascent iodine was generated by an iodide inflow into the reactor. which contained a Mixture of MA and acidic iodate. Some CO2 and a minor CO production was observed during these iodinations. It was found that in an aqueous acidic medium the produced I(2)MA is not stable but decomposes slowly to diiodoacetic acid and CO2. The first-order rate constant of the I(2)MA decarboxylation at 20 degrees C was found to be k(1) = 9 x 10(-5) s(-1), which is rather close to the rate constant of the analogous decarboxylation of dibromomalonic acid Under similar conditions (7 x 10(-5) s(-1)). From the rate of the CO2 evolution, the I(2)MA concentration call be calculated in a MA-IMA-I(2)MA mixture as only I(2)MA decarboxylates spontaneously but MA and IMA are stable. Following CO2 evolution rates, it was proven that I(2)MA can react with MA in the reversible reaction I(2)MA + MA <-> 2 IMA. The equilibrium constant of this reaction was calculated as K = 380 together with the rate constants of the forward k(2) = 6.2 x 10(-2) M(-1)s(-1) and backward k(-2) = 1.6 x 10(-4) M(-1)s(-1) reactions. The probable mechanism of the reaction is I(+1) transfer from I(2)MA to MA. The presence of I(+1) in a I(2)MA Solution is demonstrated by its reduction with ascorbic acid. To estimate the fraction of CO2 coming from the decarboxylation of I(2)MA in an oscillatory BR reaction, the oscillations were inhibited fly resorcinol. Unexpectedly, all CO2 and CO evolution was interrupted for more than one hour after injecting a small amount of resorcinol (10(-5) M initial concentration in the reactor). Finally, some implications of the newly found I(+1) transfer reactions and the surprisingly effective inhibition by resorcinol regarding the mechanism of the oscillatory BR reaction are discussed. The latter is explained by the ability of resorcinol to Scavenge free radicals including iodine atoms Without producing iodide ions.