gases and volatile liquids giving off at ordinary temperatures gases, which form explosive mixtures with air; heavy oils, which injure its burning properties, but are useful as furnishing lubricators and paraffine; tarry and carbonaceous matters; sulphur and other compounds, which give an offensive odor when burned. It is therefore refined by distillation, to separate the useful products in a pure state. The general features of the process will be best illustrated by a practical example, and for this purpose we have selected the well-known refinery of Charles Pratt & Co., at Greenpoint, Long Island, manufacturers of Pratt's Astral Oil. This establishment has a capacity of 15,000 barrels weekly.
The crude oil, coming mostly from Pennsylvania, with a specific gravity of 46 to 48° Beaumé, is run into horizontal cylindrical stills of wrought-iron, heated by anthracite fires. Eight of these stills have a capacity of 600 barrels each, and there are eight smaller ones. From these stills pipes lead to large worms, cooled by running water, and connected with a series of small tanks, so that the products from each still can be separately collected, and the successive portions that come from the still can be kept apart, according to their specific gravity.
At about 160° Fahr. (70° C.) the gases begin to come off abundantly, and these are conducted from the lower end of the worms to heat the steam-boilers. At about 225° Fahr. (107° C.) gasoline, having a specific gravity of 85° B., begins to run from the worm; after an hour and a half, at a temperature of 325° Fahr. (163° C.) naphtha begins to run, with a density of 74 B., and continues for about three hours; at 350−400° Fahr. (177−200° C.) benzine, with a density of 62° B., begins and runs about one hour. For the remainder of the heat, about thirty hours, illuminating oil is collected, with a density of 48−50° B., and ending with a temperature of 750° Fahr. (398° C.). The residuum, having a density of 20° B., is drawn off and shipped in barrels to the paraffine and lubricating oil-works. Steam is then run into the still for nearly two hours to remove the gas, the man-hole is opened, and the coke scraped off to be used for fuel.
The results of this operation are about as follows:
| Gasoline | 3 | per cent. |
| Naphtha | 10 | "" |
| Benzine | 3 | "" |
| Illuminating oil | 75 | "" |
| Residuum | 4 | "" |
| Coke and loss | 5 | "" |
| Total | 100 |
The residuum yields by subsequent treatment paraffine to the amount of about one per cent, of the crude petroleum.
The illuminating oil comes from the worm at a temperature of
