C70 



PETROLEUM, OR BOCK OIL. 



compact mass known somewhat improperly 

 as coke, and which, largely composed of earthy 

 matters and of carbon, is nearly or quite incom- 

 bustible. 



At refineries in the oil regions it is a quite 

 common practice not to separate a lubricating 

 oil, but to run off into one receptacle the entire 

 product obtained below a certain gravity at 

 the outset; while it appears that at some of 

 these the oil is cut off at about 42, and the 

 residue then mixed with crude oil and re- 

 distilled. Hence, from circumstances which 

 have now been indicated, it is often true that a 

 refined petroleum contains yet constituents 

 both too light and too heavy for use in burn- 

 ing, and so requires to be refined again. If, 

 upon testing a refined oil with the coal-oil 

 pyrometer, its vapor would explode below 110, 

 it was for some time customary to pronounce 

 such oil unsafe for burning. At present, how- 

 ever, many dealers and consumers regard as safe 

 oils of which the explosive point, correctly found, 

 is as low as 100. If a refined oil yields vapor 

 in quantities which readily explode below this 

 point, it is beyond question not suited for gen- 

 eral use as an iUuminant, but requires redistil- 

 ling, a further portion of naphtha being sepa- 

 rated. According as its naphtha has been cut 

 off at points ranging from 65 to 58 B., a 

 refined oil will show an explosive point of from 

 about 90 F. up to 115, or even to 120 or 

 more. The lower the point at which the 

 naphtha is cut off, the higher is the explosive 

 point, and up to a certain degree the greater 

 the safety of the oil, while the density of the 

 latter and its illuminating value are at the same 

 time increased. Again, if at first the petroleum 

 was distilled well-nigh or completely down to 

 a heavy residuum or to coke, more or less of 

 lubricating oil may then also be separated at 

 the last, in a second distillation. 



Through variations in the comparative purity 

 of different crude oils, and in the care of refin- 

 ing and the point to which the distillation is 

 pushed, it results that the refined petroleum 

 reaching the markets is of many grades of qual- 

 ity and value. It is evident that where much 

 heavy oil, quite or nearly colorless, can be ob- 

 tained, this will allow of retaining more of the 

 naphtha, and may yet show about a usual 

 density ; and, indeed, naphtha and heavy oil 

 are sometimes so mixed as to afford an oil hav- 

 ing the density of that of the best quality, 

 while the oil actually of such quality would 

 have its constituents more nearly in the middle 

 of the hydrocarbon series. It will thus be 

 seen that, for the quality of refined oils, density 

 alone is not a sure criterion ; as it is not, further, 

 of their safety. Thus, dealers at present de- 

 pend, for determining the quality and value of 

 refined oils, almost entirely upon their color, 

 and the indications of the fire-test ; while, for 

 crude oil, they are left to be guided in the main 

 by density alone, and for naphtha, by density 

 in connection with odor and color. Of refined 

 oils, the best quality is that known as " prime 



white," and which under the fire-test shows 

 from 115 to 120 or upward ; while after this 

 in order follow "standard white," "light straw 

 to white," "light straw," "straw," "lemon," 

 etc. These varieties of color, taken alone, aro 

 not, as has already appeared, positive tests of 

 density, of safety, or of illuminating value. The 

 fire-test now generally required in refined oils 

 for exportation, is 110 and upward ; in those 

 for home consumption, it may be stated at from 

 100 to 110. 



The burning oil obtained from petroleum has 

 in this country become generally known as 

 kerosene, although this is properly the name (as 

 originally applied by Dr. Gesner) of the anal- 

 ogous burning oil separated from crude shale or 

 coal oil. So far as burning oils are obtained from 

 petroleum, the term kerosene applied to them 

 must be regarded merely as a trade-mark, the 

 proper name, as yet, being refined petroleum. 

 Of course, in the separation of this product, no 

 rule as to the proportion which will be set aside 

 in form of the lighter and heavier constituents, 

 can be laid down for oils generally; and the 

 practice of different refiners being, as already 

 seen, quite various, considerable differences wili 

 exist in different burning oils in the respects of 

 density and the total quantity of light they 

 can afford. It has been stated that the pro- 

 portion of the limpid, merchantable illuminat- 

 ing oil, in different specimens of the crude, 

 will vary from about 30 up to 90 per cent. 

 Mr. Paul states that from crude coal and shale 

 oils not more than from 5 to 15 per cent, re- 

 quires to be separated; from Canadian petro- 

 leum not more than 10 per cent. ; and from 

 American petroleum (the writer having in 

 view, perhaps, the lighter oils from the Oil 

 Creek region) 20 to 25 per cent. He further 

 states that burning oil from coal and shales has 

 usually a specific gravity of about .825, i. e., 

 41 B., while those from petroleum have rarely 

 a specific gravity of above .800 (about 46 B.), 

 and sometimes stand as low as .780 (51 B.). 

 It is still a question, however, whether by re- 

 taining (so far as is safe) the lighter constitu- 

 ents, and so getting an oil of less density but 

 in greater volume, the total quantity of light, 

 and so, the total value obtainable from a crude 

 petroleum, is not increased. Prof. Silliman 

 quotes Mr. Gilbert as putting the loss in refin- 

 ing of crude California petroleum at 10 to 

 15 per cent., and as giving the following state- 

 ment of the products of distillation : Naphtha, 

 5 per cent., at 65 B. ; burning oil, .50, at 30 

 to 32 B. (much too low) ; light machine oil, 

 .20, at 25; heavy oil and paraffine, .25, at 

 18 B. 



Professors Brewer, of Yale College, and Whit- 

 ney, of California, appear to insist upon a radi- 

 cal distinction between the petroleum of the 

 eastern oil regions and the thick oil or mineral 

 tar of the natural wells of California; and the 

 former, at least, doubts whether this tarry oil 

 will afford good illuminating and lubricating 

 oils. Writers in California journals also have 



