The　oxidation　reaction　of　solid　hydrazodicarbonamide　with　chlorine　in　aqueous　solution　is　experimentally　studied　in　a　1　l　agitated　glass　vessel　reactor　with　a　four-blade　paddle　stirrer.　Based　on　the　film　theory,　a　model　is　first　developed　for　this　complicated　system　by　taking　account　of　the　gas-liquid　and　solid-liquid　mass　transfer,　solid　dissolution,　and　instantaneous　reaction,　especially　the　reduction　of　solid-liquid　mass　transfer　interfacial　area　arising　from　the　solid　reactant　dissolution.　The　model　can　reasonably　and　well　describe　the　experimental　data.　According　to　the　values　of　gas-liquid　and　solid-liquid　mass　transfer　coefficients　estimated　with　the　proposed　model,　it　is　found　that　the　gas-liquid　mass　transfer　is　a　rate-controlling　step　in　the　majority　of　the　reaction　course,　but　the　solid-liquid　mass　transfer　becomes　a　rate-controlling　step　when　the　reaction　is　close　to　the　final　stage　of　the　process.　©　2001　Elsevier　Science　Ltd.　All　rights　reserved.