ABSOKPTION AND PENETRATION OF COAL TAR AND CREOSOTE. 
Inasmuch as there were two 
variables in these tests, namely, 
time of treatment and 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 in most 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- 
tamed 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.) 
1.154 
50 % 
N0RM/LAR 
AMD 
50% 
CRI :os|ote 
by 
VC LU *E 
*n 
50% (ARjBOIIFItEl TAR AND *N> 
1.124 
50 7oCRE)S0Tr 
By 
V0.UIE 
) 
5 
10 
1 
5 
u."4 
• 
<ft 
Nf 
Rfc 
At, 
TA 
\k 
no 
10 
< 
1 
50 
%C 
RE 
3S0 
TE 
BY 
VOL 
UM 
E 
> 

J. 
\r 

v ^ 
50 
J 
AR 
30h 
FRK 
TA 
*A 
SJD 
50 c 
&c 
REC 
SO 
rEiv\ 
rOL 
UM 
E 
1 

1 

5 
5 10 15 
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. 
