6 BULLETIN 606, U. S. DEPARTMENT OF AGRICULTURE. 
mirror D, placed at the back of the oven, it was possible to observe 
both ends of the specimen during the test. 
The impregnation tests were made in a cylinder 1J feet in diameter 
and 4 feet long. Temperature and pressure were controlled by means 
of steam coils and a pressure pump. The specimens were separated 
from each other during treatment, so that all parts of the wood were 
in contact with the preservative. 
MATERIALS USED. 
CREOSOTE. 
The creosote used was a coal-tar product with a specific gravity of 
1.071 at 140° F. (60° C.) and a viscosity, determined by the Engler 
viscosimeter, of 1.2 at 160 c 
follows : 
F. (71° C). The distillation 1 was as 
Temperature. 
Distil- 
lation. 
° C. 
0-205 
Per cent. 
1.2 
22.7 
5.7 
9.9 
11.5 
27.6 
20.9 
.5 
205-235 
235-245 
245-275 
275-305 
305-360 
Residue 
Loss 
Total 
100.0 
The creosote was obtained by distilling a by-product coke oven 
tar (Semet Solvay) to a very hard pitch. The indices of refraction 
at 60° C. and sulphonation tests are rather low for a pure coal-tar 
creosote, probably because the tar was produced in comparatively 
low-temperature ovens. The residue was a soft, sticky pitch, indi- 
cating the presence of a small amount of undistilled tar (probably 
less than 5 per cent) . 
WOOD. 
The wood used in the experiments was selected from 25 species 
of hardwoods. In order to make the results comparable, all of the 
specimens for the different experiments on a given species were 
taken from the same log and matched as closely as possible. Most 
of the specimens used in the tests were heartwood, as sapwood speci- 
mens of sufficient size were available from only four of the species 
used. 
1 For method of analyses see Forest Service Circular 188, p. 36. 
