"Soft coal is heated in iron retorts at an intense heat. Moisture, volatile matter, and gases are driven off, coke remaining in the retort. The gases are cooled in pipes, and coal-tar condenses. then the gases are passed into a 'scrubber' where they come in contact with water, and here the ammonia dissolves. The gases pass on to be further purified from sulphur compounds by passing through calcium and iron oxides in the purifier, previous distribution as illuminating gas." -Brownlee 1907
Brownlee, Raymond B., Fuller, Robert W., Hancock, William J., Sohon, Michael D., Whitsit, Jesee E. First Principles of Chemistry (Boston: Allyn and Bacon, 1907) 180
