Conventional I-S cycle flowsheets suffer from low thermal efficiency and highly corrosive streams. To alleviate these problems, KAIST has proposed the optimal operating condition for the Bunsen reaction and devised a new flowsheet that produces highly enriched HI through spontaneous L-L phase separation and simple flash processes under low pressure. A series of experiments were performed at KAIST to validate the new flowsheet and extend its feasibility. The experimental procedure, measurement method with a rich iodine condition, and results of experiments are discussed in this paper. When the molar ratio of I(2)/H(2)SO(4) in the feed increased from 2 to 4, the molar ratio of HI/(HI + H(2)O) in the HIx phase improved from 0.157 to 0.22, which is high enough to generate highly enriched HI gas through flashing. An inverse Bunsen reaction and a sulfur formation were observed when the temperature was increased from 313 K to 343 K and the molar ratio of I(2)/H(2)SO(4) was decreased from 4 to 1. 10-50 wt% of HI in the feed turned into I(2) when an inverse Bunsen reaction and a sulfur formation occurred. The experimental data utilized in the previous parametric study of KAIST has been validated. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.