TRANSFORMATION OF SULFUR 



603 



cal agencies, especially in the presence of proper catalysts. The oxi- 

 dation of thiosulfate to tetrathionate and even to sulfate can be carried 

 out by means of inorganic catalysts, the iodine ion and peroxide being 

 sufficient for the first reaction and molybdic acid and a peroxide for 

 the second: 6 



2 S 2 3 = + H 2 2 i> S 4 6 = + 2 OH+ 



Na 2 Mo04 



S 2 3 + 4H 2 2 > 2 S0 4 = + 2 H+ + 3H 2 



The purely chemical theory of the process of sulfur oxidation has 

 been suggested. 7 With quartz sand containing iron oxide, as the me- 

 dium for the transformation of the sulfur used in the form of milk of 

 sulfur or in the colloidal form, the quantities given in table 62 were 

 oxidized. The oxidation of sulfides which took place very rapidly, 



TABLE 62 

 Formation of SO* from 200 mgm. of S in 100 grams of soil in six weeks 



especially in the case of the more soluble forms, was believed to go 

 through the sulfur stage, as shown by the following reactions: 



Fe 2 3 + 3H 2 S = Fe 2 S 2 + S + 3H 2 



Fe 2 S 2 + S + 30 + 3H 2 = Fe 2 3 -3H 2 + 3 S 



The elementary colloidal sulfur was rapidly oxidized to sulfate; the 

 rhombic sulfur, only very slightly. Kappen and Quensell themselves 

 have brought forth data to demonstrate that considerably larger 

 quantities of sulfur are oxidized in unsterile than in sterile soils. When 

 active sulfur oxidizing organisms are present, it is easy to demonstrate 

 that this process is primarily biological in nature. 



6 Abel, E. Uber katalytische Reaktionsauslese. Ztschr. Elektrochem., 18: 

 705. 1912; 19: 480. 1913. 



7 Kappen, H., and Quensell, E. Uber die Umwandlungen von Schwefel und 

 Schwefelverbindungen im Ackerboden, ein Beitrag zur Kenntnis des Schwefel- 

 Kreislaufes. Landw. Vers. Stat., 86: 1-34. 1915. 



