14 11 A standard solution was put through appropriate dilutions to give the concentrations of iron shown next The iron 11 1 10 phenanthroline complex was then formed in 25 0 mL aliquots of these solutions following which each was diluted to 50 0 mL The following absorbances 1 00 cm cells were recorded at 510 nm Fe II Concentration in Original Solutions ppm 4 00 10 0 16 0 24 0 32 0 A510 0 160 0 390 0 630 0 950 1 260