12 RULLETIN 607, U. S. DEPARTMENT OF AGRICULTURE. 



no free carbon could be detected at the magnification used. The 

 sections were further treated with chloroform and xylol separately 

 to remove the treating oils. Examination with the microscope, of 

 these resulting solutions, also failed to show the presence of free 

 carbon. 



Dr. Irving W. Bailey * has shown that extremely finely divided 

 carbon particles in certain India inks will penetrate wood, but such 

 carbon particles can not be compared with the much larger ones 

 occurring in coal tars. 



TESTS WITH MISCELLANEOUS COMMERCIAL CREOSOTES. 



Penetrance tests. — (Table 14 and fig. 6.) 



Creosotes Nos. 1 to 5 were used in experiments to determine the 

 penetrations and absorptions of miscellaneous commercial creosotes, 

 the specific gravities varied from 1.0475 to 1.105 at 60° C, thus 

 covering a wide range of oils. The method of treatment was the 

 same for each oil. Creosotes Nos. 1 and 4 contained some tar, 

 while creosotes 2 and 3 were free from tar. Figure 6 shows how the 

 tar tended to retard the penetration. It will also be noted that 

 creosotes Nos. 1 and 5, both oils being free from tar, had similar 

 absorptions and penetrations, although the specific gravity of No. 

 1 was 1.05 while No. 5 was 1.12. This shows the wide variation 

 that can exist in the specific gravity of oils free from tar, with but 

 little difference in the penetrating properties. 



INFLUENCE OF VISCOSITY. 



The viscosities of mixtures of a given tar and creosote in general 

 increased (1) as the per cent of tar was increased, (2) as the per cent 

 of free carbon was increased, (3) or as the temperature was lowered 

 and in these mixtures the absorptions and penetrations generally 

 decreased as the viscosity increased. When different tars were used 

 in the mixtures, there did not appear to be a definite relation between 

 viscosity and the absorptions or penetrations obtained. Thus in 

 figure 2, the viscosities of the three mixtures of carbon-free tars and 

 creosotes were about the same, although both penetrations and 

 absorptions vary greatly. A comparison of the viscosities of the 

 creosote-tar mixtures in Tables 4, 5, and 6, also indicates no apparent 

 relation to the absorptions and penetrations when different tars are 

 used. 



TESTS OF THE EFFECT OF VARYING TIME, PRESSURE, AND 



TEMPERATURE. 



The results of the experiments described on page 7 indicate that 

 in general the absorption and penetration of a tar and creosote mix- 

 ture decreases as the amount of tar or free carbon in the mixture is 



1 Forestry Quarterly, March, 1913. 



