Dushman/Roebuck reaction

The arsenous acid-iodate reaction is a combination of the Dushman and Roebuck reactions [145]. These reactions compete for iodine and iodide as intermediate products. A complete mathematical description has to include 14 species in the electrolyte, seven partial differential equations, six algebraic equations for acid-base equilibriums and one linear equation for the local electroneutrality. 

The iodine produced in the Dushman process is rapidly reduced to iodide via the Roebuck reaction... 

The iodate oxidation of arsenous acid is conveniently described in terms of two component processes (De Kepper et al., 1981a Hanna et al., 1982) process A, the Dushman reaction (Dushman, 1904), and process B, the Roebuck reaction (Roebuck, 1902). 

Process (VIA) is the net reaction in excess arsenite ([H3As03]o/[IOJ]0 > 3) it is equivalent to (VIB) + 3 (VIC). Process (VIB), the Dushman reaction, is normally rate determining. Therefore, the net process (VIA) is autocatalytic in [I-], which causes a dramatic color change to arise at the stoichiometric point due to the sudden appearance of I2. Bognar and Sarosi exploited this fact to devise a chronometric technique for the determination of traces of iodide43. Process (VIC), the Roebuck reaction44, has played an important role in the development of chemical kinetics and teaching of physical chemistry, as it was the first multi-step reaction for which it was shown that the quotient of the independently determined forward and reverse rate laws equals the equilibrium quotient obtained from the law of mass action. 

---