Sulfur an element of contradictions

Numerous papers contradict and appear to refute the above claims. However, an examination of these papers indicates that they are less contradictory than they first appear. Many investigators considered coal tars and a variety of different petroleum fractions produced by different processes as equivalents. Others compared the natural sulfur content of petroleum with materials to which elemental sulfur had been added. However, not all of the contradictory evidence was explained, and in some cases investigators obtained different results even though they were attempting to duplicate each others efforts. Cases where the same investigator was unable to reproduce data are known also. 

---