2SyO THE TECHNOLOGY OP SOME OF 



Persian naphtha, Burmese naphtha, &c, but it is now more exactly 

 applied to the light oil, which is the result of the action of heat in 

 organic matter. Naphtha, and its chief constituent Benzole, has, on 

 account of its numerous applications, become an important commercial 

 article and one of special manufacture from coal, shales, or some of the 

 natural tars or naphthas. The process by which it is procured from coal 

 is of this kind. Tar obtained from coal at a comparatively low tempera- 

 ture, is placed in large iron stills and distilled by direct steam. The 

 distillate constitutes " rough naphtha," is very impure and has a foul 

 odour due to the presence of a large number of organic impurities ; it 

 contains basic and acid oils and neutral hydro-carbons. To remove 

 these and purify it, the naphtha is transferred to large cylindrical 

 vessels lined with lead ; through them passes a vertical shaft capable of 

 being rotated, furnished with blades pierced with holes. Sulphuric acid 

 is now run into the vessel and mixed with the naphtha by rotation of 

 the shaft. Most of the basic oils, &c, are absorbed, and the acid of a tarry 

 consistence subsides to the bottom of the vessel and is drawn off. When 

 the naphtha is required to be highly rectified, it is a second time 

 treated with the acid. The naphtha still retains in solution the acid 

 oils, some sulphuric acid as well as sulphurous acid produced by deoxi- 

 dation. To remove these substances and effect further purity, the 

 naphtha is treated with caustic soda in an apparatus similar to that used 

 for the acid. The liquid is then distilled and constitutes the Coal Najrfitha 

 of commerce, and is mainly composed of a series of hydro-carbons, of 

 which Benzole constitutes the larger part. Benzole or Benzene (C 12 H 9 

 or C 12 H 5 , H Hydride of Phenyl) is at ordinary temperatures a clear 

 colourless liquid with a somewhat fragrant odour, and at 32° freezes to 

 a white substance like camphor. Its sp. gr. is 0.85, if it is lower, im- 

 purity or adulteration is indicated. Benzole was discovered in 1828 by 

 Prof. Faraday during some investigations into the nature of oil gas, and 

 was prepared artificially by Mitscherlisch, by the distillation of Benzoic 

 acid with lime. It boils at 177°, and this being a lower temperature 

 than the hydro-carbons with which it is associated in naphtha, pass into 

 vapour, affords a ready method of separation by fractional distillation 

 On these principles the benzole is separated from the naphtha in an 

 ingenious apparatus devised by Mr. Mansfield ; it consists of a metal 

 still of about two gallons capacity. A worm passes from the top of the 

 still through a closed cistern full of water, and communicates with a 

 discharge pipe connected with a condensing apparatus. Naphtha being 

 placed in the vessel and heat applied, nothing comes over until the 

 water in the cistern reaches 177°-, Benzole is then condensed. The pipe 

 being surrounded with water can never attain a temperature higher than 

 212°, the result is that all the hydro-carbons as toluol, cumol, cymol, 

 &c, which are not volatile at 212° are condensed and fall back into the 

 still, a second distillation keeping the head at 180° or 190° produces an 

 extremely pure article. The residue which is left in the still is by no 



