Abstract
A method for the determination of small amount of arsenic in iron and steel has been presented in which arsenic is separated by co-precipitation with manganese dioxide as arsenic(V) in nitric acid or perchloric acid solution followed by reduction to metallic arsenic with stannous chloride.
The recovery of arsenic by manganese dioxide coprecipitation was higher than 98% in nitric acid and in perchloric acid but the value was lower in the solution of mixed nitric and sulfuric acid. Titanium, niobium, tantalum and zirconium interfered and were masked by ammonium difluoride.
After the separation, manganese dioxide precipitate was dissolved in hydrochloric acid and hydrogen peroxide, boiled for about 5 minutes, and reduced by heating with stannous chloride solution (dissolving 100 g of stannous chloride in 100 ml of hydrochloric acid with 2 g of tin metal) in 9N hydrochloric acid.
The metallic arsenic was dissolved in a definite amount of N/50 standard iodine solution and titrated with N/50 standard arsenous acid solution.
As little as 0.00020.02% of arsenic in iron and steel was determined with deviation less than 0.0002%.
