Department of Chemistry, University of Jodhpur, Jodhpur Manuscript received 12 June 1972; accepted 6 April 1973 The reaction between mandelic acid and chlorine has been found to be of second order. The rate has been found to be maximum at pH~ 4.40, and is influenced by the presence of anions like sulphate, acetate and chloride. The value of energy and entropy of activation respectively are 30.4 k.cals. and 6.8 e.u. The reactive species is a combination of (HCIO+CI2) with kHCIO > kCI2. A suitable mechanism has been proposed.