23G ANNUAL OF SCIENTIFIC DISCOVERY. 



substances were capable of affording oil and oily matters, \vhen subjected to 

 dry distillation at a low tcmperatm-e ; but in general the oil obtained at the 

 first distillation comes over in a crude, coarse condition, totally unfit for use. 

 Several processes have been invented for purifying this crude oil, and some 

 of them are attended with great success ; but nearly all of them are expen- 

 sive. They involve the use of large quantities of sulphuric and other acids, 

 salts, repeated distillations, heatings, boilings, agitations, decantations, and 

 other labors. The bituminous substances before referred to, yield, on distil- 

 lation at a low temperature, a gas, which, if passed through a worm or other 

 suitable refrigerator, condenses into what is known as crude oil, requiring 

 purification, as described. 



The present invention consists in straining the gas which produces the oil, 

 by passing it through a stratum or strata of sand, or other suitable medium, 

 so that, when condensed, it forms a clear and valuable oil, ready for imme- 

 diate use. This result is obtained by the following process, viz. : The coal, 

 shale, or whatever bituminous substance is to be distilled, is broken up into 

 very small pieces, and deposited upon the bottom of the retort. Upon the 

 coal is thrown a quantity of common sand, about four times greater in 

 weight than the weight of coal. The sand should be made to cover the coal 

 evenly, so that the gas in escaping from the coal will pass through the sand. 

 A condensing tube leads from the upper part of the retort to the refrigerating 

 worm. The retort, thus prepared, is submitted to a low fire, the heat of 

 which is very gradually and carefully increased, until the coal and sand hav- 

 ing reached a temperature of about 212 Fahr., the moisture contained in the 

 coal and sand begins to rise into the condensing tube in the form of steam, 

 and on passing into the worm, is condensed into water, and escapes : the 

 water thus brought over is loaded with black carbonaceous impurities. Tho 

 same temperature being continued, the condensed water gradually becomes 

 clearer, and the oil begins to form : both oil and water escaping together 

 from the worm, the oil rising to the surface in the receiving vessel. The oil, 

 as it thus exudes, is beautifully clear and pure, and when burned in an 

 argand lamp, with a deflecting button over the wick, gives a most brilliant 

 light, totally free from smoke. As the distillation proceeds, the quantity of 

 water that conies over lessens. The temperature before named should be 

 steadily maintained until no more pure oil is produced. With some varieties 

 of bituminous substances, however, the oil ceases to come over before it has 

 all been exhausted from the material, although exposed to the above heat 

 for a time, as described ; in such cases a higher temperature is then required. 

 Such additional heat should be applied very gradually, and with the utmost 

 care. The distillation may proceed, adding degree of heat by degree, so 

 long as the distilled substance yields pure oil. When the heat has passed a 

 certain point, which is determined by the nature of the substance under dis- 

 tillation, no more pure oil can be had, and crude oily and tarry matter comes 

 over. Owing to the great variety of bituminous substances existing, it is 

 impossible to lay down the exact degree of heat required for the distillation 

 of each by the process; but as a general rule, the following method should be 

 observed : Commence with a low temperature, and carry it up very grad- 

 ually until the pure oil begins to condense; continue the same temperature 

 so long as the oil exudes. If the oil ceases, increase the heat very gradually, 

 as before described, until no more pure oil can be obtained. The gas out of 

 which the oil is formed should be set free, and have an opportunity of pass- 

 ing slowly through the filtering or straining substances, so as to deposit its 



