10 BULLETIN 145, U. S. DEPARTMENT OF AGRICULTURE. 
Satisfactory penetrations with hardwood tar, Timberasphalt, and 
sodium silicate were not secured. The results indicated that they 
were from 10 to 18 times as resistant to penetration into hemlock 
as the coal-tar creosote used. 
PERMANENCE OF THE PRESERVATIVE AFTER INJECTION INTO WOOD. 
Table 3 gives the results obtained from the volatility tests. 
After 10 weeks’ exposure the preservatives had lost amounts vary- 
ing from 1 to nearly 60 per cent. The loss was proportional to the — 
content of low-boiling oils, as shown by analysis, those having low 
distillation points losing the most by volatilization. 
The oils losing excessively by volatilization were the first two frac- 
tions of coal-tar creosote, water-gas-tar creosote (specific gravity 
1.012), and kerosene. The high volatility of these oils separates 
them from the more efficient wood preservatives. 
Those losing moderately by volatilization were coal-tar creosote 
fractions III and IV, coal-tar creosote, water-gas-tar creosote (sp. 
or. 1.051), wood tar from Douglas fir, wood-creosote oil, beechwood 
creosote, Preservol, and fuel oil. 
The least aT olerale of the oils tested were coal-tar creosote frac- 
tion VY, water-gas-tar creosote (specific gravity 1.07), Avenarius car- 
bolineum, S. P. F. carbolineum, C. A. wood preserver, hardwood tar, 
Spirittme, and Timberasphalt. Some difficulty was experienced in 
obtaining reliable data upon these oils, due to their nonvolatile 
character. There was a tendency for the specimens to absorb small 
quantities of moisture, which obscured the results somewhat. ‘The 
data show, however, that the oils just mentioned were much less . 
volatile, and therefore more permanent in the wood exposed to the 
air than those listed in the two preceding paragraphs. 
The lighter fractions of coal-tar creosote were more highly toxic 
than the very heavy fractions. It is especially necessary in the case 
of oils, therefore, that the toxic properties should be considered in 
‘conjunction with the permanence of the preservative. The higher 
toxicity and greater volatility of low-boiling creosote oils and the 
lower toxicity and lower volatility of the high-boiling creosote oils 
tend to balance each other. This point has been substantiated in 
service tests in which coal-tar creosote proved practically as efficient 
in preventing decay as the higher boiling creosote derivatives.* 
EFFECT OF THE PRESERVATIVE ON THE COMBUSTIBILITY OF WOOD. 
Table 4 gives the results obtained in the inflammability tests. 
Wood treated with the oils in every case ignited at lower tem- 
peratures than untreated wood. When permitted to air-season for 
1 See article Eng. News, Nov. 27, 1913, “Condition of experimental poles in the Augusta-Savannah and 
Helena-Meldrim lines,’’ and Forest Service Circular 198. 
