A CHEMICAL STUDY OF THE LIME-SULPHUR 
WASH.* 
L. L. VAN SLYKE, C. C. HEDGES anv A. W. BOSWORTH. 
SUMMARY. 
1. Object.— The work described in this bulletin was under- 
taken for the purposes of learning (1) how the composition of 
the lime-sulphur wash is influenced by conditions of prepara- 
tion and (2) what the composition is of various commercial 
preparations. 
2. Chemistry of lime-sulphur wash.—When sulphur and lime 
are boiled together in water, calcium and sulphur combine, 
usually forming one or two compounds, calcium pentasulphide 
(CaS,) and calcium tetrasulphide (CaS,); at the same time 
another compound is formed, known as caicium thiosulphate 
(CaS,O,), which on boiling changes into calcium sulphite 
(CaSO.) and free sulphur. Calcium sulphite on exposure to 
air changes into calcium sulphate (CaSO,). 
3. Experiments with different formulas.— Preparations were 
made containing 125 pounds of sulphur with 52, 60 and 65 
pounds, respectively, of pure lime. The general results are 
summarized as follows: 
(a) The specific gravity or density of the preparation and 
the amount of sulphur and calcium in solution increased with 
the amount of lime used. 
(b) When the largest amount of lime was used, the com- 
pound present was mostly calcium tetrasulphide (CaS,) ; when 
the smallest amount of lime was used, the mixture was more 
nearly pentasulphide (CaS,). 
(c) In the undissolved portion or sediment, free sulphur was 
present in largest amounts when the smallest amout of lime 



* A reprint of Bulletin No. 319. 
[352] 
