Abstract
A new chemical method for determination of micro amounts of sulfur in steel has been developed. It is found that H2S is easily evolved during sample dissolution with strong H3PO4 containing Fe (II) ions, and the solution absorbing H2S shows the characteristic absorption at 232 nm in ultraviolet region.
The developed apparatus is mainly consisted of reaction vessel for sample dissolution and H2S evolution, scrubbing vessel for removal of evolved water vapour and iron phosphite mist, absorption vessel for H2S and constant flowrate pump for transferring the absorbing solution to flowcell of U. V. meter.
The analytical procedure is performed as follows: 0.500 g of sample and 20 ml of strong H3PO4 containing Fe (II) ions are put into the reaction vessel. The sample is dissolved by heating in N2 stream. H2S is evolved in the reaction vessel, scrubbed with 6N HCl in the scrubbing vessel and absorbed with 5.00 ml of 0.05N NaOH. The absorbing solution is circulated through flowcell of U. V. meter by the pump. Absorbance is continuously measured at 232 nm until it becomes constant.
Above 0.5 ppm of micro amounts of sulfur can be easily determined with high accuracy. The time required for analysis of one sample is less than 10 min. The analytical results of steel samples are in good agreement with those obtained by the conventional method. Moreover, the proposed method has been improved for the higher sensitivity by concentration of sulfide ion with the anion exchange resin.
