Page:Popular Science Monthly Volume 9.djvu/171

Rh about 80° Fahr. (49° C.) and is pumped from the receiving-tank into the agitator, an immense cylindrical tank of boiler-iron, holding 1,800 barrels (a smaller one holds 500), where it is cooled (if necessary) to 60° Fahr. by water run in at the top by sprinkling from a hose, and drawn off below. Forty-four gallons of strong commercial sulphuric acid being added for every 100 barrels of oil, the mixture is agitated by air pumped in through a pipe leading down through the oil to the bottom. This is done by an engine, and produces a very thorough mixture, during which the temperature rises, and when it reaches 70° Fahr. (21° C.) the operation is ended. Water is then played upon the top for about three hours, when caustic-soda lye of 20° B. is added, in the proportion of 500 gallons to 1,800 barrels of oil, thoroughly agitated with the oil, and then drawn off at the bottom after settling. The sulphuric acid purifies the oil partly by combining with, partly by breaking up, the injurious compounds, and the soda is added to neutralize the acid. Finally, the oil is again washed with water and drawn off into bleaching-pans, of which one has a capacity of 2,000 barrels, and two others of 750 each. Here the oil is left under a roof and exposed to diffused daylight four or five hours, to improve its color, and is then removed to the storage-tanks. It is possible to expose the oil too long in the bleachers, injuring its color. It is a curious fact, noticed in several refineries, that the oil, after removal to the agitator and before treatment with the acid, sometimes gives off spontaneously inflammable gas, which has been known to take fire during the cooling with water.

The gasolene is used for making gas. The naphtha and benzine destined for the market are kept separate, but sometimes they are further treated at the refinery, and are then run together, and sent to the naphtha-works with a density of 68° to 70° B. Here they are treated in iron stills of 200 to 600 barrels capacity, heated by coal. The vapors are condensed in a series of three worms, and the operation is so managed that the various products are obtained of the required density. These products are gasolene, of 90° (sometimes 97°), 88°, and 86° B.; naphtha, of 76° and 71°; benzine, of 65° and 62°. Most of the benzine shipped is of the latter density. The barrels used for shipping all of these products are coated inside with glue.

The residuum is either "cracked" in special stills (a process of which we shall have more to say hereafter) or it is sold to be worked up for lubricating oils and paraffine.

Mr. Joshua Merrill, manufacturing chemist of the Downer Kerosene Oil Company, has made several very important discoveries in the treatment of petroleum, and a short account of them has been given in a "Memoir on Petroleum Products," communicated to the Society of Arts, Massachusetts Institute of Technology, by S. D. Hayes, March 14, 1872, from which some facts are here selected:

Neutral lubricating oil, free from offensive odors and tastes, was