Determination of microamounts of boron in iron and Steel

Abstract

According to the Methylene Blue-dichloroethane absorptiometric method for the determination ofmicroamounts of boron in iron and steel, as the blank value was high and inconstant, the method has been improved by adding a process of washing with water as follows:
Two tenths gram of sample is dissolved in 5 ml of 5N sulfuric acid and 2 ml of hydrogen peroxide (30%) in platinum crucible and an excess of hydrogen peroxide is decomposed by heating. After cooled, the residue is filtered off with a closed texture paper and polyethylene funnel, and washed with water. The filtrate is collected in a polyethylene beaker, diluted with water to about 20 ml and to it is added 5 ml of hydrofluoric acid (5%). After about one hour, the mixture is placed in polyethylene separatory funnel, diluted with water to about 50 ml, added with 3 ml of Methylene Blue solution (0.001M) and 25.0 ml of dichloroethane, and it is shaken vigorously for about one min. After being kept standing, the lower layer separated is placed in another polyethylene separatory funnel, and is added with 10 ml of water, and it is shaken vigorously for about 2 min. After the keep standing, the lower layer separated is filtered of through a dry paper and the absorbance is measured at 660 mμ against water.
The residue is fused with sodium carbonate and extracted with 5 ml of 5N sulfuric acid in a polyethylene beaker, followed by the above procedure. If chromium is remained in the residue, 2ml of ammonium ferrous sulfate solution (4%) should be added, prior to the addition of Methylene Blue solution.