Bulletin of the of Agriculture . eratures (normal amount of freecarbon in tar, 6 per cent, by weight). Time of treatment, 2 hours; pressure, 75 pounds per square inch. 20 BULLETIN 607, U. S. DEPARTMENT OF AGRICULTURE. penetration. Thus, in figure 11, the penetration at 210° F. wasabout two and one-half times that at 160° F., while the absorption PENETRANCE TESTS.(Data in Table 21.) 3 8 < Ul a. ojjg « ffi 9SORPTION- <« 1 50 r TO ii 10 1 30 2 so 2 10 2 20 TEMPERATURE—DEGREES FAR. FIG. 12.—The relation between absorptions and penetrations into longleaf
Bulletin of the of Agriculture . eratures (normal amount of freecarbon in tar, 6 per cent, by weight). Time of treatment, 2 hours; pressure, 75 pounds per square inch. 20 BULLETIN 607, U. S. DEPARTMENT OF AGRICULTURE. penetration. Thus, in figure 11, the penetration at 210° F. wasabout two and one-half times that at 160° F., while the absorption PENETRANCE TESTS.(Data in Table 21.) 3 8 < Ul a. ojjg « ffi 9SORPTION- <« 1 50 r TO ii 10 1 30 2 so 2 10 2 20 TEMPERATURE—DEGREES FAR. FIG. 12.—The relation between absorptions and penetrations into longleaf pine using a mixture of 25 percent creosote No. 4 and 75 per cent tar No. 5 at different treating temperatures. Time of treatment, 1 hour;pressure, 200 pounds per square inch. was greater. In figure 12, with a mixture containing 75 per centof tar, the penetration at 220° F. was also two and one-half times thatat 160° F., while the absorption was twice as great. Bui. 607, U. S. Dept. of Agriculture. Plate ABSORPTION AND PENETRATION OF COAL TAR AND CREOSOTE. 21 SUMMARY. The results of this investigation may be briefly summarized as fol-lows: The addition of coal tar to coal-tar creosote increased materiallythe difficulty of injection into heart longleaf pine. The resistance toimpregnation was increased as the amount of tar was to impregnation was greater to coal tars of high than tothose of low free-carbon content. This was the case even when thefree carbon was removed from these tars, indicating that the characterof the bitumens as well as the free carbon influenced tests indicate that coal tars produced at relatively low tempera-tures penetrate better than those produced at relatively high tem-peratures. The size of the free-carbon particles was also found to bea factor in penetration, as those tars in which a large proportion ofthe particles were relatively small produced mats which were morenearly impervious to the pas
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