TESTS OF WOOD PRESERVATIVES. 6 



mechanical and physical defects, was used. The pieces selected for 

 test were 12 by 26 by l\ inches. These were cut and numbered as 

 shown in A, Plate I. Some of the test specimens were left untreated; 

 others after treatment were recut and renumbered as shown in B, 

 Plate I. 



The uses to which the specimens were put are given in the de- 

 scription of each test. 



CHEMICAL AND PHYSICAL PROPERTIES OF THE PRESERVATIVES. 



The chemical composition of each preservative, its specific gravity, 

 viscosity, odor, flash, and burning points were tested by standard 

 methods. In all distillations the apparatus described in Forest 

 Service Circular 112 was used. 



The specific gravity was determined chiefly by a hydrometer or by 

 a Westphal balance. Viscosities were obtained by using the Engler 

 orifice viscosimeter at various temperatures. The flash and burning 

 points were determined by heating the preservative at a rate of 2° C. 

 per minute in an open flash-point tester, passing a small flame over 

 the surface every minute. 



METHOD OF TREATING WITH PRESERVATIVE. 



Pieces Nos. 4, 5, 6, 7, 12, 13, and 14-2 were treated with the 

 various preservatives in an impregnation cylinder. Before treatment 

 they were oven-dried at 100° C. in order to be sure that all speci- 

 mens were as nearly as possible in a uniform moisture condition. 

 They were then weighed and impregnated. The simplest proce- 

 dure of treatment was followed. For example: After the wood 

 was placed in the cylinder the preservative was admitted, displacing 

 the air, until the cylinder was completely filled; a pressure of about 

 50 pounds per square inch was then applied until the desired absorp- 

 tion was obtained, when the cylinder was drained of excess preserva- 

 tive and the specimens removed and weighed within 24 hours. When 

 necessary higher pressures than 50 pounds were used. 



STRENGTH TESTS. 



Pieces 1, 2, and 3, which were not treated, and 4, 5, and 6 (see 

 A, PI. I), which were treated with the preservative, were tested in 

 bending to failure in an ordinary 30,000-pound testing machine, 

 using a center load over a 12-inch span. Care was taken to have all 

 specimens at approximately the same moisture content at the time 

 of test (about 6 per cent) by allowing them to remain in the laboratory 

 until they no longer absorbed moisture from the air. Specimens 

 treated with oils usually contained a little less moisture than those 

 untreated. After being broken, 3-inch specimens were cut from each 

 end for fungus-pit tests (see B, PI. I). 



