Sulfur and its inorganic compounds

The mode of action of elemental sulfur has been investigated in great detail since it came into use. The first theories were based on the physical properties of sulfur. 

Electricity generated upon contact of sulfur with the plant (Mangini, 1871) and the sun-ray collecting lens effect (Mach, 1879) were the first attempts to explain the fungitoxic effect of sulfur. Subsequently, attempts were made to clarify the role of the water-soluble compounds of sulfur, and in this period only Sempio (1932) was a proponent of the direct effect of sulfur. 

Elemental sulfur is a hydrophobic substance, practically insoluble in water. It was formerly thought that sulfur could not permeate the fungal cells, but needed first be converted into a water-soluble form. Two possibilities were given oxidation or reduction. 

Several theories were also propounded on the action of sulfur within the fungal cell. Initially, enzymatic processes were suggested, in which sulfur reacts with 

The activity of the different allotropic forms of sulfur has also been investigated with respect to permeation. Feichtmeir (1949) demonstrated that amorphous sulfur is about three times as active as crystalline sulfur of comparable particle size. 

---

Kelley, K. K., Contributions to the data on theoretical metallurgy VII. The thermodynamic properties of sulfur and its inorganic compounds. U.S. Bur. Mines Bull., 406, 1937. 

---