FINAL SUMMARY REPORT. 71 



itself is one of the most stable of hydrocarbons and would probably 

 be the last to undergo any change. It was for a long time thought 

 that bitumen and asphalt were oxidised products of various hydro- 

 carbons and contained oxygen, 1 but Mr. Clifford Richardson has 

 shown that oxygen is not a constituent of asphalt to any appreci- 

 able extent, while sulphur is. 2 He found that asphalt consists chiefly 

 of unsaturated hydrocarbons and is characterised by the presence 

 of mercaptans and other sulphur derivatives. He concluded that 

 asphalt " does not originate as such, but is a secondary product, 

 resulting from the transformation of lighter forms of bitumen, 

 malthas, or even thinner oils, into harder bitumen by condensation 

 and polymerization, a reaction in which sulphur seems to' take an 



important part Xo high temperatures seem necessary for the 



change once initiated, as it is seen going on to-day in the Trinidad 

 Pitch Lake and in Venezuela. Gas is commonly evolved and is 

 largely hydrogen sulphide, the natural result of the condensation 

 of hydrocarbons by sulphur. Carbonic acid accompanies it which 

 would seem to point to a reaction between hydrocarbons and 

 inorganic sulphates and the latter as the source of the sulphur 

 in the bitumen of asphalts.'' 3 He goes on to say, however, that 

 " this is only theory based on the presence of sulphates in the water 

 emulsified with Trinidad pitch, while there is quite as much hy- 

 drogen sulphide given off by the Bermudez asphalt which contains 

 no water or sulphates as it originates." In the Mesopotamian seep- 

 ages the accompaniment of sulphate-bearing water is very common 

 but not invariable or at any rate not continuous. It seems to me 

 highly probable that some of the less stable hydrocarbon members 

 break down by the action of calcium sulphate in some such way as 

 Holer's formulae depict, producing hydrogen sulphide and carbo- 

 nate of lime. Sometimes all the carbon dioxide is not taken up by 

 the lime and portions of it escape in seepage and oil-well waters. 

 Mr. Sherburne Rogers found this gas very frequently in the waters 

 of the Coalinga oilfield. The hydrogen sulphide also partially 

 escapes as such and is partially taken up by the hydrocarbons 

 to form sulphur derivatives. Polymerization accompanies all these 

 processes and the total result appears to be exothermic, since a 

 slightly raised temperature usually characterises sulphur-bearing 



1 Dana's " Mineralogy." 



i Joum. Soc. Chem. Industry, Vol. XVII, p. 30 (1898). 



3 loc. cit, p. 31. 



