酸化鉄
This process also has intermediate reactions, and as such, the phosphate rock created has impurities. One such impurity—and the most important one—is iron oxide. Iron oxide impurities are reduced and form iron phosphides. The resulting second liquid product is called ferrophosphorus. Iron is considered an impurity and undesirable because it requires additional carbon and power for reduction. Thus, it locks up a certain percentage of the phosphorus.