Volume 10, Issue 2 (March 1982)
Explanation of the Empirical Factor Recommended in the Permanganate Titration of High Chromium Stainless Steel from Tristumulus Chromaticity
Excess results of 0.6% are obtained for chromium in high chromium steels when analyzed according to the ASTM Chemical Analysis of Steel, Cast Iron, Open-Hearth Iron, and Wrought Iron (E 30). The excess results have been explained on the basis on the tristimulus chromaticity of the human photocell, that is, the eye. It is concluded that the 0.6% excess results are necessary because: (1) 6% of the excess is for the permanganate pink to show itself in colorless solution, (2) 30% of the excess is for the permanganate pink to overcome the green hue of the chromium and nickel sulfates present in the solution, and (3) the balance 64% of the excess is needed because of the oxidation of trivalent chromium by permanganate. The trichromatic coordinates of nickel sulfate and chromium sulfate solutions have been calculated both according to Commission Intérnationale d' Eclairage (CIE) 1931 recommendations, namely, x,y coordinates and also according to a perceptually more uniform chromatic system of color matching, that is, u,v coordinates.