1. The conditions affecting the accuracy of sulfur determination by barium chloride precipitation have been studied, using potassium and sodium sulfates.

2. The effect of sodium, calcium and magnesium salts has been investigated, under conditions approximating those of insecticide analysis.

3. A definite set of conditions is quoted, which if strictly observed, will yield fairly accurate analyses. For more accurate work, a method of checking by analysis of a synthetic solution is advocated.

4. The theory of the contamination of barium sulfate by extraneous substances is discussed, and the experimental data throw further light upon the nature of the adhesion phenomena.

5. An exhaustive bibliography of previous work is appended, together with abstracts of the papers.