16 
BULLETIN 607, U. S. DEPARTMENT OF AGRICULTURE. 
longitudinal penetration of about 17 per cent resulted from the 
increase in the proportion of tar. 
When the mixture containing 33 J per cent of tar was used, it was 
noted that after the specimens had been treated for a certain length 
of time (see Table 15. footnote) no increase in the absorption was 
obtained. Hence it was not possible in this test (where the tem- 
perature of the preservative was 160° F. and the pressure 80 pounds 
per square inch) to obtain an absorption with the mixture equal to 
that obtained with the creosote, even when the time of treatment 
was increased to eight hours. The average longitudinal penetration 
was about 33 per cent less than obtained with the creosote. 
PENETRANCE TESTS. 
(Data in Tables 16 and 17.) 
AVE. LONGITUDINAL PENETRATIOH-IMS. TIME OF TREATMENT - HRS. 
AVE.ABSORPTIOH-LBS. 
6789 PI 2345678 
0.02 0^6 0.10 
60% CRE0. 
20% TAR 
* 6«.?SCRE0. 
33.3| TAR 
*IT*aS MOT POSSIBLE TO 0BT«1« THE QEOVIREB 
AESOAPTlOa WITH THIS MIXTVftt 45 * FUBTKEH 
WCBEASE 1M THE TIME OF TStATHENT 010 ROT 
OrCBtftSE THE iiK»«T(» 
TIME GF TREATMENT VARIED 
fcVE.LOHfiJTUDIHALPEHETRATION-IWS, AVE. PRESSURE- LBS. PER SQ. IN, 
AVE. ABSORPTION -LBS. 
3 12 3 4 5 6 7 8 9 40 80 120 160 O.02 O.06 0.10 0.14 
PRESSURE VARIED 
Fig. S.— The relative effect of varying (1) time of treatment and (2) pressure in order to secure approxi- 
mately the same absorption in longleaf pine using mixtures of tar No. 4 and creosote No. 6. With time 
varied the treating temperature was 160° F. and the pressure SO pounds per square inch. With pressure 
varied the time of treatment was 2 hours and the temperature 160° F. 
Time of treatment and temperature of preservative constant and pres- 
sure varied. — (Tables 16 and 17 and fig. 8.) 
The specimens used in these tests were matched with those just pre- 
ceding, and hence the results are directly comparable. The pressure 
required to obtain a given absorption in the test in which the tempera- 
ture of the preservative and the time were constant was approximately 
proportional to the amount of the tar in the mixture. With almost the 
same absorption of preservative the penetrations of the two tar and 
creosote mixtures were from 27 to 29 per cent less than those obtained 
