1991 Volume 77 Issue 11 Pages 1902-1907
The blue species of molybdosilicic acid and molybdophosphoric acid are strongly adsorbed on Sephadex gels, i. e., over 70% of blue species in a 100 ml colored solution is concentrated in 0.2 g of Sephadex G-25 within a half hour. Gel-phase colorimetry, based on the direct measurement of a gel-phase, which has adsorbed the blue species, has been applied to the microdetermination of silicon and phosphorous in iron and steel. The optimum condition for color development in the gel-phase has been examined on the basis of the procedure in JIS G 1212 for silicon and in JIS G 1214 for phosphorous. The colored gels were packed into a 2-mm cell. The absorbances at 810 and 500 nm for silicon and at 810 and 450 nm for phosphorous were measured using a reference of water-swollen gel. And the difference of absorbances was used for the determination of trace of silicon and phosphorous. Silicon and phosphorous at ppm-level in iron and steel could be determined by the present method.
