COAL-TAR AND WATER-GAS TAR CREOSOTES. 
51 
VAPOR PRESSURE. 
In the course of some experimental runs made by the Forest 
Service in a wood-preserving plant of light design, an explosion 
occurred which resulted in the rupture of the cylinder. It was 
thought at the time that, if the vapor pressure of the creosote oil 
were found to be sufficiently great, it might be an important factor 
in determining the design of treating plants. Experiments were 
therefore made to ascertain this vapor pressure at least approximately. 
Table 15 shows the average results obtained in experiments with two 
creosotes of different characteristics. 
Table 
15. — Vapor pressure of coal-tar creosotes. 
Vapor pressure. 
Vapor pressure. 
Temper- 
Temper- 
ature 
ature 
(degrees 
Inches 
Pounds 
(degrees 
Inches 
Pounds 
C). 
of 
per 
C). 
of 
per 
mercury. 
sq. in. 
mercury. 
sq. in. 
50 
2.0 
1.0 
no 
7.4 
3.7 
60 
2.8 
1.4 
120 
8.2 
4.1 
70 
3.6 
1.8 
130 
9.0 
4.5 
80 
4.6 
2.3 
140 
9.8 
4.9 
90 
5.6 
2.8 
150 
10.6 
5.3 
100 
6.4 
3.2 
This vapor pressure is not sufficient to do any material harm, 
since it is always less than the atmospheric pressures at ordinary 
temperatures and elevations. If, however, the creosote contains 
water, the vapor pressure under this condition will be the sum of the 
vapor pressures of creosote and water. The vapor pressure of the 
mixture will be as shown in Table 16 if the vapor pressure of creosote, 
as given above, is used: 
Table 16. — Vapor pressure of mixtures of coal-tar creosote and water. 
Vapor pressure. 
Vapor pressure. 
Temper- 
ature 
Temper- 
ature 
(degrees 
Inches 
Pounds 
(degrees 
Inches 
Pounds 
C). 
of 
per 
C). 
of 
per 
mercury. 
sq. in. 
mercury. 
sq. in. 
40 
3.0 
1.5 
80 
18.6 
9.3 
.50 
3.5 
2.7 
90 
26.2 
13.1 
60 
8.6 
4.3 
100 
36.4 
18.2 
70 
12.8 
6.4 
In this case, even at 100° C, the vapor pressure in excess of atmos- 
pheric pressure (15 pounds a square inch) is only 3.2 pounds a square 
inch, which is a pressure so small that it need not be taken into 
consideration in designing treating plants. 
SPECIFIC HEAT. 
It is frequently desiraole to know the specific heat of creosote in 
order that allowance may be made for sufficient coils to heat the 
