67 



1. Elementary sulphur occurs dissolved in some Texas oils 

 and separates as crystals in the tanks. 



2. Hydrogen sulphide appears as traces in some Galician 

 and Canadian oils. 



3. Mercaptans or sulphur (thio) -alcohols are found in oils 

 noted for their sulphur content, as the Persian, Mexican and 

 Egyptian. 



4 Alkyl-sulphides of thio-ethers and disulphides are noted 

 for the difficulty attending their removal. 



5 and 6. The last two definite classes to be mentioned are 

 the thiophanes cited previously and the thiophenes. In the 

 light of recent research on the synthesis of the thiophanes it 

 appears that they are analogous to the homocyclic Cycloparaffins 

 or Naphthenes mentioned earlier (p. 62) in this paper. The 

 thiophanes are in fact heterocyclic paraffins in which the 

 polymethylene rings are closed by sulphur. Just as the homocyclic 

 naphthenes range from the 3-methylene ring up to 7 or 8 methy- 

 lene rings, so the thiophanes range from 4-membered rings up 

 to a 7-ring. (Grishkew T itch-Trochimovski, Tourr. Russ. Phys. 

 Chem. Soc, 1916). The thiophenes contain less hydrogen than 

 the thiophanes, but so far all attempts made to hydro= 

 genate the thiophenes to 5-membered thiophanes by the 

 ordinary methods, using finely divided nickel or platinum, 

 have failed, possibly as a result of the poisonous action sulphur 

 has upon these catalysts. The thiophenes and the coupled thio- 

 phenes, the thiophthenes, form a class wh:ch is represented by 

 small quantities in different oils- The tetra-substituted thiophenes 

 may play a part in the chemistry of Kimmeridge oil and will be 

 discussed more fully a little later. 



One class of sulphur compounds still remains to be mentioned, 

 which, though having no chemical designation of its own, always 

 plays a very important part in the development of an oil field or 

 shale deposit, as for example that of the Kimmeridge formation, 

 until the problem of the nature of the sulphur compounds found 

 in them is solved and the class can be placed amongst the known 

 types or a new type made to receive it, as was the case with the 

 thiophanes. This, the great class of undefined sulphur compounds* 

 holds the puzzle of the Kimmeridge shale. Research is now pro 

 ceeding in several quarters, and no doubt ultimately the experi- 

 ences of the Ohio Lima oils will be repeated in this country, and 

 the Kimmeridge oil shale, from being merely a potential source of 

 oil, will become an actual source. 



Turning now to the question of the removal of the sulphur 

 constituents from oils it must be borne in mind that the problem 

 means the task in each case to find the proper key to fit a given 

 lock. In other words research is necessary to find out what par- 

 ticular type of sulphur compounds constitutes the harmful impuri- 

 ties and then a suitable chemical treatment is adopted to remove 



