Answer to Question #141720 in General Chemistry for Iulia

Question

by what method are the iron impurities in the reagents determined? and how to determine Iron impurities in reagents

Answer 1

Method to determines IRON impurities is atomic absorption spectropotometer or spectrophotometric method for the determination of iron (III) impurities....

A commonly used method for the determination of trace amounts of iron involves the complexation of Fe²⁺ with 1,10-phenanthroline (phen) to produce an intensely red orange colored complex: Fe²⁺ + 3 phen ----> Fe(phen)₃ ²⁺ .Since the iron present in the water or any solution predominantly exists as Fe3+, it is necessary to first reduce Fe³⁺ to Fe²⁺. This is accomplished by the addition of the reducing agent hydroxylamine. An excess of reducing agent is needed to maintain iron in the +2 state (because dissolved oxygen will reoxidize Fe²⁺ to Fe³⁺). Fe²⁺ is quantitatively complexed by 1,10-phenanthroline in the pH range from 3 to 9. Sodium acetate is used as a buffer to maintain a constant pH at 3.5. If the pH is too high, the Fe²⁺ will be oxidized to Fe³⁺; if the pH is too low, H+ will compete with Fe²⁺ for the basic 1,10-phenanthroline (to form phen H+ ). Either way, you won’t get complete complexation. The determination of the iron-phen complex is performed with a spectrophotometer at a fixed wavelength of 508 nm using external calibration based on iron standard solutions.