10 BULLETIN 145, U. S. DEPARTMENT OF AGRICULTURE. 



Satisfactory penetrations with hardwood tar, Tirnberasphalt, 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. 

 gr. 1.051), wood tar from Douglas fir, wood-creosote oil, beechwood 

 creosote, Preservol, and fuel oil. 



The least volatile of the oils tested were coal-tar creosote frac- 

 tion V, water-gas-tar creosote (specific gravity 1.07), Avenarius car- 

 bolineum, S. P. F. carbolineum, C. A. wood preserver, hardwood tar, 

 Spirittine, and Tirnberasphalt. 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. 1 



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-Meldrirn lines," and Forest Service Circular 198. 



