Coal under high temperature at 1150 ℃ in the purified air stream combustion, various forms of sulfur in coal are decomposed by combustion, is the air flow into the electrolytic cell and water combine to form H2SO3, destroyed the electrolytic cell because of its original Some iodine - iodine ions on the dynamic equilibrium, the device will immediately generate the output current electrolysis of iodine potassium iodide solution to restore the original dynamic equilibrium, which is GB/T214-1996 the coulometric titration. Specific dynamic balance back to the original number of consumed current, is decomposition of coal combustion is directly related to the amount of sulfur, which can be measured and calculated by the microprocessor, and therefore we can draw the sulfur content in coal