PETROLEUM. 151 



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 oif 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 mixt- 

 ure, 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 neu- 

 tralize the acid. Finally, the oil is again washed with water and 

 drawn off into bleaching-pans, of w T hich 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 opera- 

 tion is so managed that the various products are obtained of the re- 

 quired 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 Kero- 

 sene 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 



