160 , PURIFICATION OF PETROLEAN OILS. 



will continue to increase until a cheap and successful process is discovered 

 for their decarbonisation. 



The methods practised by persons engaged in refining the American 

 petroleums are as different as those in use for the purification of the oils 

 distilled from coal. Some employ acids and alkalies, others use alkalies 

 alone, and steam is applied at various degrees of heat. Some of the 

 oils produced by those means are of good quality, others are inferior, 

 and do not ascend the wick of the lamp in sufficient quantities to afford 

 a constant light. In others, the illuminating principle, by some change 

 effected on the carbon, is partially destroyed, and in almost all the odour 

 is disagreeable. The oils from some of the wells contain traces of chlo" 

 ride of sodium, otheis carbonate of soda in quantities sufficient to affect 

 their treatment. The denser oils, or those which contain too much 

 carbon to admit of being consumed in lamps without smoke, are excellent 

 lubricators, either mixed or unmixed with animal oils. 



It will be perceived by the foregoing statement that it would be a 

 difficult task to prescribe a mode of purification to meet the requirements 

 of the oil-refiners. Neither the petroleums, nor the oils distilled from 

 them, contain creosote, or carbolic acid, and other impurities which 

 contaminate the oils distilled from coals and coal shales, their purification, 

 therefore, is simple and comparatively cheap. 



When the proof of the oil is not below 38°, distillation with water, 

 or by the use of steam, will most frequently render the lamp-oil of good 

 colour, and its illuminating properties will be of the highest order. 

 Before the heavy oils, or those below the proof of 38°, are submitted to 

 any treatment, it is necessary to give them a preliminary distillation, by 

 the aid of common or superheated steam, and the distillate should be 

 separated into two parts, all below proof 38° being set aside to be treated 

 for lubricating oil, and a farther portion to be added to the illuminating 

 oil. Washing a lighter part of the charge with a solution of caustic 

 potash, or soda of specific gravity not exceeding 1,400, is useful. A final 

 distillation over a weak solution of either of those alkalies will generally 

 render the oil pure. The heavy parts of the oil may require agitation 

 with equal parts of sulphuric acid and water, followed by an alkaline 

 wash, and then distillation. It is only the most impure oils, and those 

 from the wells of certain localities, that require the use of acids, which, 

 like the strong alkalies, when used in excess, greatly impair the illu- 

 minating properties of these hydro-carbons. The lighter the oils the 

 lighter the colour. At proof 45" they are colourless. At proof 42° 

 colouring matter begins to appear in the distillate, and continues to in- 

 crease until the charge is exhausted. In order to present the lamp-oil of 

 a light colour, some refiners have sent it to the market at proof 45°; but 

 it should be understood that such oils are much more inflammable and 

 liable to explode than those at proof 40°. Colour, in this instance, 

 should be sacrificed to safety. The offensive odour of these oils is re- 

 moved by the means laid down for the deodorisation of coal oils. A 



