Modern Gasworks Practice

548 MODERN GASWORKS PRACTICE to atmospheric temperature for the complete extraction of are re-heated before passing into the saturator. and w o ul d be greatly r e d u c e d were it possible to maintain the oxide of iron in a fit con-dition. Otlier points requiring attention in Order to make the semi-direct pro-cess a success are the entire elimination of all tarry matter from the crude gas, and the maintenance of the acid bath. at such, a temperature as to permit of the formation of the salt. In general, there are two alternative p r o -cesses. In one the tar is separated at a temperature just above dew-point, the gases being con-ducted directly into the saturator, and the liquor in the saturator being maintained at a temperature so as to permit of sul-phate manufacture by the application of external heat. A more successful method, however, is that in which the gases are cooled tar, after which they