Bunsen reaction is an important step of sulfur iodine cycle for hydrogen production from thermochemical splitting of water. Polyiodide species generated during the separation process need to be identified for complete understanding of the mechanism involved. Speciation of these polyiodide species formed during Bunsen reaction can lead to better understanding of kinetics of the process. HIx species formed have been analyzed using UV-visible and Raman spectroscopic techniques. Peak corresponding to HI3 species have been ascertained and their conversion to higher HI5, HI7 ...... species has been observed. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.