30 BULLETIN 102, VOL. 1, UNITED STATES NATIONAL MUSEUM. 



THE RESOURCE. 



NATURB. 



Petroleum, or crude petroleum as the raw or unrefined product is 

 often termed, is an oily liquid varying considerably in appearance 

 according to the locality from which it comes. It is an extremely 

 complex mixture of organic compounds, chiefly hydrocarbons,^ but 

 substances containing sulphur, oxygen, and nitrogen are also present 

 in small amounts. It contains, therefore, five chemical elements of 

 the first importance in life processes, a circumstance that suggests 

 at once an organic origin and determines the important role that 

 this substance is due to play in filling the needs of man.^ 



If crude petroleum is exposed to the air, it gradually thickens until 

 a solid residue is left. The first product given off is natural gas; 

 then liquid components evaporate in the order of their lightness ; and 

 the final residue is composed largely of either paraffin wax or as- 

 phalt. Petroleum is thus seen to be a mixture of different liquids 

 dissolved in on^^another and holding in solution also natural gas and 

 solid substances. This conception correlates natural gas as a by- 

 product of petroleum^ and affords a simple epitome of the changes 

 more rapidly induced when petroleum is subjected to refining.* The 

 asphalt lake of Trinidad and the ozokerite deposits of Galicia and 

 Utah represent natural residues from the prolonged evaporation or 

 natural distillation of petroleum. 



While petroleums vary considerably in character, they fall chiefly 

 into two classes according to whether the residue yielded is pre- 

 dominantly paraffin wax or asphalt.^ This broad distinction is of 

 great economic significance, because the paraffin petroleums, occur- 

 ring chiefly in the eastern part of the country, came first into use 

 and therefore determined the current refining practice and the exist- 

 ing demand for petroleum products; while the asphaltic petroleums, 

 exploited later in the Gulf region and California, found their imme- 

 diate commercial outlet in the form of fuel. The higher gasoline 

 content of paraffin oils, coupled with the distance of coal from the 

 Californian region," gave free scope to the economic differentiation 

 of the two types. 



^ Compounds composed of hydrogen and carbon. These substances are present by the 

 hundreds. 



2 It would be shortsighted to assume that petroleum even now has displayed Its full 

 measure of versatility. 



3 Part of the natural gas production of the country, indeed, comes from petroleum 

 wells. 



* The processes of refining, of course, involve some chemical changes also. 



^The first are said to have a paraffin l)ase; the second, an asphaltic iase, or called 

 merely asphaltic petroleums. There are also intermediate oils with almost equal pro- 

 portions of paraflln and asphalt. 



8 The presence of coal fields in California, however, would have scarcely deterred the 

 development of the oil fields of that State, although their presence would afford a pleas- 

 ing contemplation now. 



