Stability and safety of parenteral 57 Fe solutions Prior to i.v. administration to the infants the 57FeSO4 solution will be tested for pyrogenicity, sterility, and stability. Limulus amoebocyte lysate (LAL) testing and repeated culture for bacterial and fungal growth to confirm that the 57FeSO4 solutions are pyrogen-free and sterile at the concentrations to be used in the study. The nutrient content of the parenteral solutions has been previously described. The total iron content of the 57FeSO4 -nutrient solution will be determined by atomic absorption spectrometry before and after filtration (0.22 µ filters), and over time at room temperature.