PROTECTING WOODS AGAINST TERMITES. 



11 



treated timber by the writer indicate that the " open-tank " method 

 of impregnation with coal-tar creosote renders wood resistant to 

 attack by wood-boring insects for at least 15 years. Treating of 

 wood by this method can be done with homemade apparatus (PI. I, 

 fig. 4) , using unskilled labor. The timber should be well seasoned 

 before impregnation, however, and the treating should be very care- 

 fully done; a uniform penetration should be secured, sufficiently 

 deep to allow for season checking ; this is especially necessary if the 

 treated timber is to be set in warm climates. 



Impregnation treatments by the more technical pressure pro- 

 cesses are the most effective, as well as the most costly, but the results 

 usually justify the extra cost. Inspections of treated timber by the 

 writer indicate that impregnation by the full-cell pressure process 

 will render wood resistant for at least 25 years. 



The results of the tests of the comparative effectiveness of the 

 superficial methods of treating timber in protecting it against at- 

 tack by termites are given in Figure 3 and Table 4, while the re- 

 sults of the impregnation treatments are given in Table 5. 



Table 4. — Results of tests of the relative effectiveness in preventing attack by 

 termites of miscellaneous superficial chemical preservative treatments for 

 crude or finished forest products. 



Preservative. 



Method of application. ^f^lf 00 * 1 



Effectiveness. 



Liquid M, a volatile yellow fluid, 2 per 

 cent solution. 



"Ebonizing," chromic acid and aniline 



oil. 

 Liquid S, a yellowish oily liquid with a 



strong varnish odor. 



Preservative T, a preservative paint 



Oil S, a creosote oil made from coni- 

 ferous wood. 



Oil C, a very light gravity brown oil, 

 containing much tar, acids, and water. 



Both brushing, 2 coats 

 applied hot, and 

 dipping. 



Brushing, applied hot. 



Both brushing, 2 coats 

 (one week between 

 coats), and dipping. 



Both brushing and 

 soaking. 



Brushing 



.do. 



Yellow pine 



Ash and yellow 



pine. 

 Yellow pine , 



Ash , 



Chestnut , 



do , 



Failure after 4 

 months. 



Failure after 5 



months. 

 Failure after 6 



months. 



Failure after 1 



year. 1 

 Effective for less 



than 5 years. 1 

 Do. 1 



1 Period when first examination was made after setting. 



Table 5. — Results of tests of methods of impregnating woods with preservatives 

 to prevent attack by termites, 1913 to 1922. 



Treatment. 



Results. 



Full-cell pressure process: 



Commercial wood creosote (No. 126) , tested with yellow pine 



Commercial coal-tar creosote (No. 154). tested with yellow pine 



Coal-tar creosote oil A , tested with yellow pine 



Coal-tar creosote oil B , tested with yellow pine 



Steaming for various periods under different pressures, tested with ash 



Empty-cell pressure process, using yellow pine for test: 



Commercial wood creosote (No. 126) 



Commercial coal-tar creosote (No. 154) 



Coal-tar creosote oil A 



Coal-tar creosote oil B 



Open-tank process, using yellow pine for test: 



Commercial wood creosote (No. 126) 



Commercial coal-tar creosote (No. 154) .' 



Coal-tar creosote oil A 



Coal-tar creosote oil B 



Boiled in iron sulphate solution for 2 hours, then plunged in copper sulphate 

 solution and left for 2 hours. 



1 Period when first examined after placed in test. 



No failures. 



Do. 



Do. 



Do. 

 Failure after 6 

 months. 1 



5 failures out of 12 



in 1922. 

 No failures. 



Do. 



Do. 



1 failure in 1916; 5 

 failures out of 12 

 in 1922. 

 No failures. 

 Do. 

 Do. 

 Failure after 5 

 years. 



