Journal . hichis gas-fired, and the upper still is the one in which the hot vapourspass through a large coil to dehydrate the tar contained therein,ready for the next distillation. The stills can either be fired withsolid fuel or gas, but towards the end of the distillation steam isalways used in an interior coil for better control. In this opera-tion of distilling, like others, advantage is taken of the differentboiling points. A good thermometer is therefore inserted so thatthe temperature of the contents can be watched. The first vapours which pass off at a temperature from 88° to17(i C. ar
Journal . hichis gas-fired, and the upper still is the one in which the hot vapourspass through a large coil to dehydrate the tar contained therein,ready for the next distillation. The stills can either be fired withsolid fuel or gas, but towards the end of the distillation steam isalways used in an interior coil for better control. In this opera-tion of distilling, like others, advantage is taken of the differentboiling points. A good thermometer is therefore inserted so thatthe temperature of the contents can be watched. The first vapours which pass off at a temperature from 88° to17(i C. are a little ammonia water and some light spirit. At170° C. practically all the light oil has passed off. The receiverinto which the distillate has been flowing is now changed, and thetemperature increased steadily to 230° C. during which time themiddle oil is distilled off, and run into a second receiver. Thetemperature is then increased from 230° to 270° C. to get off the 164 COAL AND ITS Fig. 3.—View of Benzole Rectification Plant, Back of Stillsand Condensers. COAL AND ITS BY-PRODUCTS. 165 creosote oil, which is run into a third receiver. The temperatureis again increased above 270° C. to get off the heavy or anthraceneoil, which is run into a fourth receiver, and during the time theanthracene oil is coming off steam has to be added to the still. Instead of running the condensed liquids direct into receiversit is better to run them into pans to allow naphthalene and anthra-cene crystals to settle out before running the oils into thereceivers. Summary. Temperature at which they are distilled. Ammonia liquor Up to 100° C. Ligutoil „ 170° C. Middle oil Between 170° C. and 230° C. Creosote oil „ 230° C. „ 270 C. Heavy or anthracene ,, 270° C. ,, 350° C. The tar distiller knows by experience when to stop the dis-tillation somewhere between 300° C. and 350° C, according to thequality of the residual pitch required which is left in the sti
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Keywords: ., bookcentury1800, bookdecade186, bookpublisherlondon, bookyear1861
