Spectrophotometric Determination of Manganese in Iron and Steel by Decomposition with Perchloric Acid.

Abstract

As a spectrophotometric method of manganese in iron and steel the (NH₄)₂S₂O₈ method has been mainly adopted.In this method, the sample is decomposed by a mixture of nitric acid, sulphuric acid and, phosphoric acid.
The authors studied the (NH₄) ₂S₂O₈ method using perchloric acidic solution which decomposed the sample. It is said that conversion of Mn⁺² into Mn⁺⁷ by only perchloric acidic solution is commonly unstable.
After studying all kinds of method, authors found this method to be good as far as the amount of perchloric acid in this colored solution is 2 to 10ml.
The features of this method are as follows:
(1) The sample solution is easily converted into Mn⁺⁷ from Mn⁺² by heating in the boiling bath for only 2 to 3 minutes.
(2) Sufficient addition of color reagent is AgNO₃ solution (0.5%) 10ml.and (NH₄)₂S₂O₈ solution (15%) 10ml.and a color develops rapidly.
(3) Color of Mn⁺⁷ is stable for a day.
(4) The sample containing a large amount of nickel, chromium and cobalt can easily be determined, too.