Sour Water
From Captain of Industry Wiki
Sour Water is a liquid product which is a byproduct of refining Crude Oil in the Distillation (Stage I). The Sour Water Stripper is the primary means of obtaining Sulfur for the production of Rubber and Acid before the Sulfur Mine is discovered and repaired, as well as the primary source of Ammonia for the production of Fertilizer from petrochemical means.
Sour Water is also produced as a byproduct when cracking Naphtha in the Cracking Unit to generate Diesel.