PETROLEUM, OR ROCK OH, 



C69 



the oils of higher gravity. On Dnck Creek, O., 

 wells very near each other sometimes show a 

 difference of 10 B. in the gravity of the oils 

 they afford ; and this fact is of course paralleled 

 in many other locations. 



General statements place the crnde oil 'of 

 Oil Creek, as the rule, at gravities of from 40 D 

 up to 47 D , and sometimes 50 B. (sp. gr., .829 to 

 .785) ; about Franklin, at 30 to 32 (sp. gr., 

 .879 to .869) ; of Burning Spring Run, at 33 3 

 to 41 (sp. gr., .864 to .825) ; about Horse Xeck 

 Run, at 28 D to 42 D (sp. gr., .890 to .820) ; about 

 Cow Ran, 0., at 40 to 41 ; at Mecca, O., at 

 26 to 28" (sp. gr., .901 to .890). Prof. Andrews 

 states that oil from the coal measures may vary 

 in gravity from 20 to 52 3 B. (sp. gr., .936 to 

 He also speaks of a crude oil from near 

 Pomeroy, O., which shows 51 B. (.781), and 

 burns freely and with a brilliant flame, without 

 refining. 



The temperature fixed by custom as the 

 standard for testing the gravity of rock and 

 coal oils, crude and refined, is 60 D F. As at 

 temperatures below this the density of the oil is 

 increased, while at those above it becomes more 

 rare, it is necessary, in testing oils at other 

 temperatures than 60, either to make allow- 

 ance for the difference, or to bring a sample to 

 the standard temperature. Buyers now require 

 that a fair sample of any tank or lot of crude 

 petroleum in question shall be brought to the 

 standard temperature before testing. 



As among the important chemical properties 

 of petroleum, it may be remarked that the oil 

 crude or refined does not unite or properly 

 blend with water, though it imparts to the lat- 

 ter its peculiar smell and taste. It combines in 

 all proportions, however, with strong alcohol, 

 with ether, and with common oils, both the 

 essential and the nnctnous. It dissolves sulphur, 

 phosphorus, iodine, camphor, most resins, wax, 

 and fats, and softens rubber into a glairy var- 

 nish. These qualities serve to explain some of 

 its uses yet to be named. (UEE'S Dictionary.) 



Refining of Petroleum : Separation into Dis- 

 tinct Products. TVhile standing in tanks, the 

 crude oil loses much of the gas it may have held 

 as brought up from the wells. It also loses by 

 evaporation, and to a greater extent as it is al- 

 lowed to stand longer, portions of its lower or 

 most volatile constituent hydrocarbons. Where 

 the oil is raised by pumping, the jet of gas is 

 often visible as it shoots out horizontally from 

 the pump, with each discharge of oil ; and 

 over the tanks into which oil just raised has 

 been run, it is not uncommon to see a sort of 

 tremulous or glimmering appearance, like that 

 sometimes observed where heated air is rising, 

 and due to the presence of a scarcely visible 

 cloud of escaped oil-vapors. In consequence 

 of the rapidity with which the evaporation 

 sometimes goes on from light oils when first 

 raised, the remaining body of such oil is, in 

 some cases, cooled almost or quite to freezing. 

 Almost any crude oil, however, will still retain 

 some portion of gas and of the lightest con- 



stituents, as well as usually some water, an4 

 of course, other impurities. 



To free the crude oil from remaining admix- 

 tures such as those already named, is one object 

 of the refining process; another is. at the same 

 time, to separate from one another though not 

 in an exact and perfect manner certain groups 

 of the entire series of component hydrocarbons, 

 each group intended to contain such of these 

 as are suited to some particular use or uses. 

 The groups so separated constitute so many 

 complex materials, somewhat differing in their 

 composition, and in certain of their sensible 

 qualities. The means of such separation are 

 afforded in the successively higher boiling points 

 of the component oils, and in the circumstance 

 that some of the constituent hydrocarbons are in 

 reality solids, and which the oily components 

 merely hold in solution. 



Thus, in order to obtain from petroleum a 

 suitable burning oil, it is necessary to cut off 

 both the extremes of the hydrocarbon series. 

 The points of separation in the series could be 

 determined by the density of the oil as it is car- 

 ried over from the still, or perhaps by tempera- 

 tures. In refining and separating the burning 

 oil, in this country, the points 01 cutting off are 

 usually determined, the lower by the density, 

 and the higher by the same, or by the color of 

 the oil flowing from the still. Thus, as the heat 

 imparted to the crude petroleum placed in the 

 still is gradually raised, the portion which at 

 first distils over, and above a point of gravity 

 which different refiners take variously at from 

 about 65 down to 58 B. as tested, of course, 

 by bringing samples to 60 F. is set aside, and 

 constitutes the crude naphtha. It is most com- 

 mon to cut off the naphtha at some point in a 

 range of from 63 to 59 B. Many refiners 

 separate first of all the lightest naphtha, down 

 to about 80' B. ; to this the name of gasolene has 

 been given. In the first refining of petroleum, 

 the practice in determining the point of cutting 

 off at last, i. e., from the heavier components, 

 is perhaps still more various. It appears that 

 in some refineries a separation is at once made 

 between the burning oil proper and a denser or 

 lubricating oil ; and those who desire to pro- 

 duce a refined petroleum of the best qualities, 

 collect the oil for such purpose toward the last 

 no longer than it continues to run "light," or, at 

 farthest, a (whiter) " light straw ; " or, when de- 

 termined by density, to about 42 to 35 B. If 

 beyond such point the distillation be kept up, and 

 the product separately collected, this will consist 

 of a lubricating oil, but which also holds some 

 parafKne. Here, again, the distillation may be 

 stopped while the thicker residue in the still, 

 and which is commonly known as the residuum, 

 is yet only of the consistency of very thick oil 

 or of a fluid tar ; and in such case, the residuum 

 will still contain much parafiine and some lubri- 

 cating oil. In other cases, the first distillation 

 in refining petroleum is kept up so long as any 

 dark and heavy oil continues to go over ; and 

 the only residue st the last is then the hard and 



