ABSORPTION AND PENETRATION OP COAL TAR AND CREOSOTE. 



Inasmuch as there were two 

 variables in these tests, namely, 

 time of treatmentand the pressure, 

 it was necessary to consider both 

 of these factors ; hence, the product 

 of pressure and time has been used 

 in the data presented. The tests 

 were made at a higher temperature 

 and pressure than were the pene- 

 trance tests but the mixtures were 

 the same. In making the tests 

 the temperature was kept con- 

 stant. 



The addition of tar made neces- 

 sary the use of increased pressure 

 or time of treatment or both to 

 obtain the same absorption of 

 preservative as was obtained with 

 creosote. 



After the tests, the blocks were 

 split to determine the penetration 

 and inmost cases they were found 

 to be fairly well penetrated when 

 given an absorption of 16 pounds 

 per cubic foot. However, a tend- 

 ency to variation in penetration 

 was greater in the blocks treated 

 with the heavier and more viscous 

 tarmixtures. Unpenetra ted areas 

 were found near the centers of 

 some of the blocks which had 

 been treated with preservatives 

 containing 75 per cent and 100 

 per cent of tar. 



MIXTURES OF CREOSOTE AND TAR WITH 

 VARYING AMOUNTS OF FREE CARBON. 



Penetrance tests. — (Tables 4, 8, 9 

 and 10 and figs. 2 and 4.) 

 The curves shown in figure 4 in- 

 dicate that the influence of free 

 carbon on penetration and absorp- 

 tion was greatest in the mixture 

 made from tar No. 1, which con- 

 tained normally 6 per cent of 

 free carbon. 



The curves also indicate that 

 with an increase in the percentage 

 11917°— 18— Bull. 607 2 



PENETRANCE TESTS. 

 (Data in Table 4.) 



































































1164 

































































































o 

































b 

































. 1.154 



U. 































































O 

































H- 

























L 1 



AR 



AMD 



> 

















50 



% 



norm; 



| 1.144 



EC 















SK'J&rRI'OSBTI BY V<LUilE 

































































Ll 

































































V) 













































































































































>0% (ARjBOUFIIEE TARA|ND 

















50° / oCRE^>S0TE 



BY 



VOLUME 















































































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5 



NORMAL PERCENT OF FREE CARBON IN MIXTURE BY WEIGHT 



Fig. 2.— The relative absorptions and penetrations 

 into longleaf pine of mixtures of equal propor- 

 tions of creosote (No. 4) and three different tars 

 (Nos. 1, 2, and 3). Two mixtures were made of 

 each tar. The free carbon was removed from the 

 tar in one mixture and the other contained the 

 normal amount of free carbon. Time of treat- 

 ment, 2 hours; pressure, 75 pounds per square 

 inch; temperature of preservative, 160° F. 



