42 THE IRON ORE DISTRICT OF EAST TEXAS. 



order to avoid the repeated distillation necessary according to the old pro- 

 cess, the tar is subjected to a treatment with sulphuric acid, and after separ- 

 ation from the acid is distilled over hydrate of lime; the paraffine obtained 

 by crystallization and for purification is pressed with white lignite tar. This 

 process, by avoiding a second distillation and the decomposition caused there- 

 by, yields a superior article and a larger amount of paraffine. 



MINERAL OIL. 



Since the discovery of the large North American oil fields, the product ob- 

 tained from them has gradually, and now almost entirely, supplanted the oils 

 artificially produced from lignites. At present there is hardly a single 

 factory in the world in which the production of these oils from brown coal 

 forms the main object. However, as they frequently constitute side-products 

 in the various branches of the brown coal industry, their qualities remain of 

 interest, and will be briefly noticed. 



The mineral oil proper is a clear, colorless, thin liquid, gradually assuming 

 a yellowish color, of moderately strong, though not very agreeable, odor. It 

 burns without soot in lamps constructed for the purpose. 



The solar oil possesses a similar, though somewhat different, odor, is clear 

 and colorless after distillation, but turns brownish on keeping. It is used 

 successfully for illuminating purposes in suitable lamps. 



The lubricating oil is of an iridescent brownish or greenish color, has the 

 consistency of a heavy oil, and possesses a weak and not disagreeable odor. 



GAS. 

 The manufacture of illuminating gas from brown coal is an industry of 

 considerable importance. Experience proves that smelting works and fac- 

 tories which are located in the lignitic region can employ such plants with 

 profit. As early as 1859 Tashe published a number of experiments con- 

 ducted on a large scale at his factory in Salzhausen by Nidda, in Hesse, 

 Germany, and even at that date expressed his opinion that a profitable utili- 

 zation of lignites for the manufacture of illuminating gas was beyond all 

 doubt. He obtained three hundred and fifteen cubic feet of gas from one 

 hundred pounds of brown coal in small fragments. In the same year Kohl- 

 mann used lignite tar in the manufacture of gas, and his experiments were 

 very successfully repeated in 1866 by Rouvel, who pronounced the gas to be 

 possessed of high lighting power, simple and cheap in its manufacture, and 

 valuable for small as well as for large establishments. Walker and Smith 

 add that the gas is of far superior quality to that produced from common 

 stone coal, and preferable for house use on account of the absence of sulphur, 

 better lighting power, lower rate of consumption, and less heating effect. 

 They produced in their factory at Egeln one hundred and ten cubic feet of 



