Journal . content of thetar to 1 %, and to reduce the free carbon, butneither the volatile low-boiling hydrocarbons(benzene and toluene) nor the tar acids are re-moved. The distillation process is free from theabove objections. Compared with the continuousdistillation process, the intermittent process hastlie disadvantage that it requires skilled attentionand that there is considerable danger of the tarfrothing and boiling over during the earlier portof the distillation. distining tar until the residue has the temperature-specified below :—(1) For road spi-aying, 230° C. :(2) for tar macadam,
Journal . content of thetar to 1 %, and to reduce the free carbon, butneither the volatile low-boiling hydrocarbons(benzene and toluene) nor the tar acids are re-moved. The distillation process is free from theabove objections. Compared with the continuousdistillation process, the intermittent process hastlie disadvantage that it requires skilled attentionand that there is considerable danger of the tarfrothing and boiling over during the earlier portof the distillation. distining tar until the residue has the temperature-specified below :—(1) For road spi-aying, 230° C. :(2) for tar macadam, 260° ; (3) for pitch °. Follo\Wng are the approximate yields oftar products, but the figures vary slightly accordingto the quality of the tar. Road Board specifl_a- tion. No. 1. Xo. 2,Xo. 3. Working tempera-ture. 230° ° C,288° C. Quantity ^/^•^?^t^r 90% I 9%distilled, ™i,^ ^^.benzol per toluol per gallons, toiiof tar.!* f of tar. 2934 VACOLJRPiJE rTr^skp COKDEN5IHC. Three qualities of prepared tar are specifiedby the Road Board and may be obtained by Ten tons of crude tar if dehydrated will produce300 gallons of light oils, giving, on gallons of crude carbolic acid. 25 gallons ofcresylic acid. 30 gallons of 90% benzol, 20 gallons-of 90 % toluol, 40 gallons of solvent naphtha, and150 gallons of light creosote oil. The , and Hammond continuous dehydrationplant shown in the figiire is stated to get overthe difficulty of removing the water from crudetar. The danger of boiling over can ))e obviatedby ha-^-ing only a shallow layer of tar in the a large vapour space above it. The tarenters by the crude tar inlet into the condenserand serves to cool the vapours from the still. Itthen jDasses through the heat interchanger andthence into the still, through which it passes in atortuous coiuse and, having been deprived of itswater and light oil. overflows through the heatinterchanger to the dehydrated tar store.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectchemist, bookyear1882
