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HISTORICAL SURVEY
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moisture, led through a wet Cottrell system to remove SO3 mist, and finally dried through a drying tower. The dried and cleaned gas is then passed into the vanadium contact mass through a system of heat exchangers. From the vanadium converters, the gases are led through
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Fig. 3. Diagram of LeBlanc soda industries.
absorption towers to make 98-99 per cent H2SO4 or 105-109 per cent oleum.
If the utilization of such waste gases for the manufacture of sulfuric acid Is not sufficient to take care of all the gases available, due perhaps to the limited demand for sulfuric acid in the country, the remaining waste gases may be converted to elemental sulfur, not by the LeBlanc procedure,
