Rapid determination of sulfur in rocks

Sulfur is determined turbidimetrically as barium sulfate after an aqua regia attack. The turbidity is formed in an ammoniacal solution from which R2O3 has been centrifuged. Reproducibility of turbidity is obtained by adding barium chloride as a solid rather than as a solution. Sulfur is determined in the range 0.01-4 percent within ±0.02 absolute, or approximately 5 percent of the amount present, whichever is larger. A 100-mg sample is used for sulfur concentrations of up to 0.50 percent S, a 20-mg sample for higher levels. A determination requires about 5 minutes.