Coal Gas

—A complex hydrocarbon gas, containing about 90% of hydrogen and marsh gas, and 5% of heavy carburetted hydrogen and acetylene. It is produced from the destructive distillation of coal, heated out of contact with air, in iron or fire clay retorts. The products of distillation are first cooled in condensers to free them of suspended coal tar and ammoniacal liquor; are then pa ed through scrubbers, or towers filled with wet coke, to di olve out the ammonia; next through purifiers in which trays of slaked lime or ferric oxy hydrate absorb sulphur and carbon dioxide from the gas; finally being stored in a gasometer, preparatory to distribution as an illuminant.