74 
BULLETIN 1036, U. S. DEPARTMENT OF AGRICULTURE. 
VOLATILITY. 
The volatility of three water-gas-tar creosotes is shown in figure 
3 Id. Here the loss by volatilization is plotted against the percentage 
distilling at 270° C. These data were obtained from hemlock treated 
with water-gas-tar creosotes and held under test for 80 days at a 
temperature of 40° C. The conditions of these tests were the same 
as those described in connection with figure 31b, for coal-tar creosotes. 
The same general result is obtained from these creosotes as from 
coal-tar creosote, namely, that the volatility increases in some direct 
ratio to the percentage distilling below 270° C. The character of the 
test, whether from open pan or 
from treated wood, whether of 
short or long exposure, and the 
temperature of heating will, of 
course, affect the volatility in the 
same general manner as in coal-tar 
creosote. Different results would 
probably also be obtained if dif- 
ferent species of wood were used. 
A comparison of the two curves, 
which are comparable as far as 
treatment, wood, temperature of 
heating, and length of exposure 
are concerned, reveals the fact that 
the volatility of water-gas-tar creo- 
sote is the same as that of coal- 
tar creosote having the same per- 
centage of distillate below 270° C. 
It follows, therefore, that the dis- 
cussion of the volatility of coal- 
tar creosotes will apply equally 
well to water-gas-tar creosotes. 
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Fig. 35. — Change in viscosity of water-gas-tar 
creosotes with change in temperature. 1. 
Very high boiling oil. 2. Similar to a high- 
boiling creosote. 3. Low-boiling oil. 
VISCOSITY 
The change in viscositv with a 
rise in temperature for three water- 
gas-tar creosotes of widely different characteristics is shown in 
figure 35. The creosotes are pure distilled products without the 
addition of any tar. The change in viscosity of water-gas-tar creo- 
sotes with change in temperature can be calculated in the same 
manner as that of coal-tar creosotes according to the equation, 
V 
-7pX= K, where Fis the absolute viscosity, Tthe absolute temperature, 
and K and A are constants depending upon the oil. The equations, 
