Determination of Tin in Steel, Pig Iron, Alloy Steels and Iron Ore

Abstract

In order to control the amount of tin as an impurity in steel, rapid methods of its estimation have been investigated and found that the following method gave good result. The sample (2.5 g) is decomposed with 40 ml HNO3 (1 : 1), 10 ml 5 % MnSO4 and water are added to make up to about 350 ml, 3 ml 3 % KMnO4 is added dropwise while boiling with 2 ml additional KMnO4 after the formation of MnO2 and the KMnO4 is decomposed; the precipitate is filtered off, washed with hot water, decomposed with 20 ml HCl (1 : 1) and a small amount of 3 % H2O2, diluted to 100 ml with water, boiled with 50 ml HCl (d. 1. 18) and 50 ml H2SO4 (1 : 1) to decompose the H2O2, cooled, 1 ml saturated HgCl2 solution and 5 g NaH2PO2 are added, boiled for 5 minutes in CO2, cooled to 10°C, titrated with N/60 iodine solution and the amount of Sn is calculated by substracting the value from the blank titration. This method is not affected by the presence of Cu and Cr, up to 12.5 mg of Ti, Mo and W, also the effect of V is avoided by reprecipitating the MnO2 and that of As is avoided by filtering off metallic As formed by the reduction of Sn. The tin in steel, pig iron, alloy steel, and iron ore (since the Sn in the ore is insoluble in acid, a fusion method with Na2O2 is employed) is estimated with the accuracy of 0.001 % and 0.01 % in iron ore, and the time required for estimation is 28-38 minutes for carbon steel, and 36-62 minutes for iron ores.