Chemical State Analysis of Sulfur in Blast-furnace Slags

Abstract

A new method for chemical state analysis of sulfur in blast-furnace slags has been developed. The outline of the procedure is as follows. A slag sample was powdered with a neutral solution containing zinc acetate for 10 min in a disk mill in order to prepare a suspension of fine slag particles without air oxidation. The suspension was filtered and then the zinc sulfide on the filter was dissolved with acetic acid and standard iodine solution. Then, excess iodine was titrated with standard thiosulfate solution to deter mine the amount of sulfide (MS). Formalin and acetic acid were added to, the filtrate of the suspension and then it was titrated with standard iodine solution to determine the amount of thiosulfate (MS₂O₃). The filtrate was heated after the addition of hydrochloric acid and zinc, and then the amount of sulfate (MSO₄) was determined by a barium sulfate gravimetric method.
This proposed method was successfully applied to the determination of states of sulfur in slags. The coefficients of variations of MS(0.49% S), MS₂O₃(0.092% S) and MSO₄(0.072% S) were 1.54%, 2.63 %, and 3.82%, respectively, The sum total of the sulfur occurring in various states, (S, MS, MS₂O₃, MSO₄) in blast-furnace slags, as determined by this proposed method, agreed well with the total sulfur content obtained by the conventional combustion-iodometric method.