TESTS OF WOOD PRESERVATIVES. y 



PHYSICAL AND CHEMICAL PROPERTIES. 



The results of the tests on physical and chemical properties are 

 given in Table 1 . 



EFFECT OF THE PRESERVATIVE ON THE STRENGTH OF WOOD. 



Table 2 gives the results of the tests on the effect of the preservative 

 on the strength of wood. 



As a greater accuracy than plus or minus 10 per cent could not be 

 obtained in these tests, largely because of variables inherent in wood, 

 the conclusions should be interpreted liberally. 



All of the preserving oils, viz, the products of coal tar, wood tars, 

 water-gas tars, and crude petroleum produced no appreciable weaken- 

 ing in the strength of the wood impregnated with them. The amount 

 of moisture which the treated specimens contained could not be 

 definitely determined, although it is believed that it was slightly less 

 than the moisture in the untreated specimen. The variations in 

 individual cases from the average is within the limit of accuracy of 

 the test. An average of all the tests indicates that the strengths 

 treated and untreated were about the same. 



In general, the water-soluble preservatives caused a slight weak- 

 ening of the seasoned wood. This was most pronounced in the case 

 of sodium silicate and by-product zinc sulphate. The values given 

 for the effect of these preservatives are accentuated, due to the 

 higher moisture content of the treated pieces. The application of a 

 moisture-correction factor would probably show that, with the ex- 

 ception of sodium silicate and by-product zinc sulphate, the weaken- 

 ing caused by the water-soluble preservatives is of no practical 

 significance. The specimens treated with sodium silicate, however, 

 were noticeably affected, the outer wood fibers being badly checked 

 and disintegrated. 



PENETRANCE OF THE PRESERVATIVE INTO WOOD. 



Table 2 gives the results obtained on the penetrance of the preserv- 

 ative into wood. 



So far as penetrance is concerned, the following preservatives can 

 be considered satisfactory: Coal-tar creosote, coal-tar creosote frac- 

 tions I, II, III, and IV, the three water-gas-tar creosotes, S. P. F. and 

 Avenarius carbolineums, C. A. wood preserver, beechwood creosote, 

 Spirittine, wood-creosote oil, copperized oil, fuel oil, kerosene, zinc 

 chloride, commercial zinc sulphate, by-product zinc sulphate, B. M. 

 preservative, sodium fluoride, and cresol calcium. 



Wood tar from Douglas fir, Preservol, and coal-tar creosote fraction 

 V were very difficult to force through hemlock, being more than 

 twice as resistant as coal-tar creosote. 

 58293°— Bull. 145—15 2 



