Phase separation is of major importance in a Bunsen reaction in sulfur-iodine thermochemical cycle for hydrogen generation. Extensive experimental data on Bunsen reaction was collected and assembled over range of reaction temperature 293 -393.5 K, excess iodine in the range of 1-16 moles, and excess water in the range of 1-22 moles. The data was systematically analyzed to see key parametric effects on the reaction. The effects of iodine, water and temperature were studied on density ratio, distribution of components in two phases, reverse Bunsen reaction, SO2 dissolution, and azeotrope limits. Best operating conditions were obtained to for which Bunsen reaction would be economical. The analysis indicated that iodine excess of 4 to 6 moles, water excess of 10.5 to 12.5 moles, and temperature range of 345-360 K are the best operating range for the Bunsen reaction. These operating ranges ensure no side reaction, economical operation by avoiding excess iodine, water and complicated options to break or bypass azeotrope. In addition reverse Bunsen and SO2 solubility study are also considered for better understanding of process. Based on this study unique points of operation are recommended.