12 BULLETIN 607, U. S. DEPARTMENT OE 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 1 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 hi coal tars. 
TESTS WITH MISCELLANEOUS COMMERCIAL CREOSOTES. 
Penetrance tests. — (Table 14 and fig. 6.) 
Creosotes Xos. 1 to 5 were used hi 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 Xos. 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 Xos. 1 and 5, both oils being free from tar, had similar 
absorptions and penetrations, although the specific gravity of Xo. 
1 was 1.05 while Xo. 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 
hi 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. 
T«STS 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. 
