ABSORPTION AND PENETRATION OF COAL TAR AND CREOSOTE. 23 
APPENDIX. 
DETAILED DESCRIPTION OF TESTS. 
Penetrance tests. — Each, specimen before test was placed on a shelf 
in the oven of the penetrance apparatus and the temperature main- 
tained at 160° F. for 24 hours. 
A hole 1 inch in diameter and either f or 1 inch deep was bored 
in the specimen. The piece was weighed to 0.001 of a pound imme- 
diately before and after treatment. The absorption of preservative 
by each specimen was determined from the difference in weights. 
About 24 hours after treatment each specimen was sawed longitudi- 
nally and transversely through the center of the hole on the lines 
indicated in figure 13. The treated areas shown on the surface thus 
exposed were measured by means of a planimeter and the average 
longitudinal penetrations determined from these measurements. 
Impregnation tests. — The blocks were air-dried in the laboratory for 
several months; consequently they had a very small moisture con- 
tent. Before treatment each block was weighed to 0.01 of a pound 
and the dimensions measured to 0.01 of an inch. The volume was 
Fig. 13.— Appearance of test pieces. 
determined from these measurements. After treatment each block 
was again weighed and the absorption in pounds per cubic foot 
computed. 
APPARATUS. 
The " penetrance apparatus/' illustrated in figure 14, was designed 
for the penetrance tests. The wood under test, which, had a 1-inch 
hole bored in it, figure 13, was clamped against the open end of the 
pipe A leading to the bottom of a pressure tank B. The pipe and 
lower portion of the tank were filled with the preservative. Pipe C, 
opening into the top of the tank, was connected with an air reservoir. 
When desired, air under pressure was turned into tank B, which thus 
placed the preservative under pressure. The apparatus was sur- 
rounded by a wooden oven R, with double glass windows in the front 
and back. Steam coils J in the bottom of the oven heated the speci- 
mens and preservatives to a uniform temperature, which duplicated 
as nearly as possible the temperature conditions of the treating cylin- 
der. The pressure was determined from the gauge G and the tem- 
perature from thermometer H. A safety valve K aided in maintain- 
ing a uniform pressure. Shelves were provided and specimens were 
