159 



An Evolution Method for the Determination of Sulfur 

 in Sulfides and Sulfates. 



By Frank C. Mathers. 



The object of this research was to devise a rapid method for the 

 estimation of sulfur in sulfates and sulfides, especially in the presence of 

 such elements as molybdenum, which interfere with the precipitation of 

 barium sulfate. The idea was to heat the material with some metal which 

 would reduce all of the oxidized sulfur and then combine with it to form 

 a sulfide. The rest of the method would coincide with the ordinary volu- 

 metric evolution method for sulfur in iron and steel. 



Powdered potassium sulfate, containing 18.39 per cent, of sulfur, was 

 used in these experiments. In each experiment, 0.2 gm. of the potassium 

 sulfate was thoroughly mixed with the reducing metal and was placed in 

 a crucible which was heated. Experiments with zinc dust as a reducing 

 agent showed that it was impossible to reduce all of the sulfate at low tem- 

 peratures and that at higher temperatures some sulfur was lost by volatili- 

 zation along with the zinc. 



Gms. of Zn Per cent, of S Per cent, of S in 

 Used. Temperature. Evolved. the Residue. 



3.0 Bunsen burner, 5 minutes. 17.05 0.64 



3.0 Blast, 5 minutes. 17.20 0.11 



The use of a mixture of zinc and aluminum gave still poorer results. 

 The addition of bases such as calcium oxide, calcium carbonate, sodium 

 carbonate, or magnesium oxide were without beneficial effects. The use 

 of some charcoal did not help. 



Magnesium turnings gave the best l'esults. To protect the porcelain 

 crucibles, they were partly filled with 1.5 gms. of magnesium oxide and a 

 cavity was made in this with the end of a test tube. The charge was placed 

 in this cavity and was covered with 0.5 gm. of magnesium oxide. The por- 

 celain crucibles, with well fitting lids, were heated for 5 minutes with a 



