ORGANIC SULFUR-COMPOUNDS RESULTING FROM THE INTERACTION OF IRON SULFIDE, HYDROGEN-SULFIDE AND CARBON-DIOXIDE IN AN ANAEROBIC AQUEOUS ENVIRONMENT

The reaction of iron sulfide (FeS) with H2S in water, in presence of C O2 under anaerobic conditions was found to yield H-2 and a variety of organic sulfur compounds, mainly thiols and small amounts of CS2 and d imethyldisulfide. The same compounds were produced when H2S was replac ed by HCl, in the H2S-generating system FeS/HCl/CO2. The identificatio n of the products was confirmed by GC-MS analyses and the incorporatio n of H-2 in the organic sulfur compounds was demonstrated by experimen ts in which all hydrogen compounds were replaced by deuterium compound s. Generation of H-2 and the synthesis of thiols were both dependent u pon the relative abundance of FeS and HCl or H2S, i.e. the FeS/HCl- or FeS/H2S-proportions. Whether thiols or CS2 were formed as the main pr oducts depended also on the FeS/HCl-ratio: All conditions which create a H-2 deficiency were found to initiate a proportional increase in th e amount of CS2. The quantities of H-2 and thiols generated depended o n temperature: the production of H-2 was significantly accelerated fro m 50 degrees C onward and thiol synthesis above 75 degrees C. The yiel d of thiols increased with the amount of FeS and HCl (H2S), given a ce rtain FeS/HCl-ratio and a surplus of CO2. A deficiency of CO2 results in lower thiol systhesis. The end product, pyrite (FeS2), was found to appear as a silvery granular layer floating on the aqueous surface. T he identity of the thiols was confirmed by mass spectrometry, and the reduction of CO2 demonstrated by the determination of deuterium incorp oration with DCl and D2O. The described reactions can principally proc eed under the conditions comparable to those obtaining around submarin e hydrothermal vents, or the global situation about 4 billion years ag o, before the dawn of life, and could replace the need for a reducing atmosphere on the primitive earth.