1973 Volume 22 Issue 7 Pages 886-892
There is Japanese Industrial Standard : JIS M 8212 for the determination of total iron, in which trivalent iron is reduced with stannous chloride and the excess of reductant is oxidized with mercuric chloride. However, it is known that this method is undesirable in view of the pollution of the drain age by mercury. For this reason, the authors proposed the using of metallic aluminum in place of stannous chloride as reductant of iron. The aluminum reduction method have already been reported by Scott (Ref. 3), Riegel (Ref. 4) and Wakino (Ref. 5), but this method was very restricted. about the application for interference element. Titanium gave a serious error, and this method can not be adapted to samples which contain titanium. For determination of iron in various samples by aluminum reduction method, it was necessary to remove the interference of titanium. In the proposed method, such an interference could be masked by titrating the tungsten blue, which was formed from reduced trivalent titanium and sodium tungstate, with potassium dichromate solution. Subsequently, iron in this solution was titrated with standard potassium dichromate solution.
Three methods, acid dissolution method, direct fusion method with sodium peroxide and fusion method with potassium phyrosulfate, for the determination of total iron have been experimented. The procedure of acid dissolution method is as follows:
0.4 g of sample is dissolved with 30 ml of hydrochloric acid in a reducing flask by heating. The solution is diluted to 150 ml with water after adding 10 ml of hydrochloric acid. After addition of 1.5 g of granular aluminum, the solution is heated gently until it is dissolved in nitrogen gas for reduction of ferric iron. The solution is cooled in a cooling water to a room temperature passing the nitrogen gas. 30 ml of the sulfuric acid-phosphoric acid mixture and sodium tungstate solution are added and then the solution is diluted to about 250 ml with cold water. To prevent the interference by titanium, the solution is titrated with 0.1 N potassium dichromate solution until the blue color of the solution is disappeared. Subsequently, bivalent iron in the solution is titrated with standard potassium dichromate solution using the sodium diphenylamine sulfonate as the indicator and iron content is determined.
Analytical results of raw materials for iron manufacture by this method agreed closely with those by stannous chloride method and standard deviation for hematite, sinter and iron are were 0.04, 0.07 and 0.06, respectively.
