Technical paper . This warming is accomplishedby merely decreasing the supply of feed water to the condenser. The next or fourth fraction to come over is called creosote, dead oil, or heavy oil, and is usually the last fraction is not always the last fraction, however, for sometimes an an-thracene fraction, otherwise included in the creosote, is collected. OPERATION AND CONTPvOL. 17 The properties of creosote depend largely on the completeness oftlie distillation. AVhen soft pitch is desired as a residue from dis-tillation, the volume of creosote will be smaller and there will beu
Technical paper . This warming is accomplishedby merely decreasing the supply of feed water to the condenser. The next or fourth fraction to come over is called creosote, dead oil, or heavy oil, and is usually the last fraction is not always the last fraction, however, for sometimes an an-thracene fraction, otherwise included in the creosote, is collected. OPERATION AND CONTPvOL. 17 The properties of creosote depend largely on the completeness oftlie distillation. AVhen soft pitch is desired as a residue from dis-tillation, the volume of creosote will be smaller and there will beusually but a small amount of solid matter crystallizing from it atordinary room temperature (G0° to 70° F.). If hard pitch is made,the volume of this last fraction is greater, as the distillation is carriedfurther, the distillate coming over during this later stage beingchiefly solid at G0° F.; hence the proportion of solids in the creosoteis greater when the distillation is carried to a hard pitch. The color. Figure 4.—Pitch-cooling tank used in small plants: a, Draw-off valve; b, steam coil; c, steam inlet to coil. of the first part of the creosote fraction is amber, gradually chang-ing as distillation proceeds to a dark amber or amber red. The solidpart, if collected separately, is greenish brown or olive and residue in the still—pitch—is drawn off and then cooled in acooling tank (see fig. 4) to a temperature suitable for tank is covered to keep out rain and snow and has a steam coilfor heating the pitch, in case it should become too cold before bar-reling. The pitch is then drawn off into tight, dry, open-headed bar-rels, in which it solidifies on further cooling and in which it is usu-ally shipped. In the larger plants, however, where a very hard50456°—21 2 18 TAR AXD ITS SIMPLE CRUDE grade of pitch is made, the latter is generally drawn off into a spe-cially provided pool in the open air where it is stored. When a distil
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