WOOD SOIL COST ACT CULTURE TECHNIQUE 



127 



would be fi.xed in the wood and thus resist leaching when exposed to the action 

 of ground waters. 



The second type is comprised of organic compounds or mi.xtures of organic 

 compounds, such as creosote, which has had an excellent service record as a 

 preservative. Also included in tliis type of comi)ounds (which are insoluble 

 in water and have a relatively low vapor pressure) are certain chlorinated 

 phenols and cresols. Because of the low water solubility or immiscibility 

 with agar solutions, the uniform dispersal of the toxic agents in the agar 

 system, which is essential to reproducibility of results, is ahnost impossible. 

 Uniform injection of these materials into wood, however, presents no par- 

 ticular problem. 



Assays of four representative mixtures not readily assayable in the petri 

 dish are included in the results of Table 3. The composition of the treating 

 solutions of the mixtures 1, 2, 3, and 4 is given below: 



In the assays shown in Table 3 the maximum retention of the mixture by 

 the wood is that recommended for the treatment of wood that is not to be 

 used in contact with the ground. To make the test as severe as possible, 

 organisms were selected which were known from petri dish, koUe flask, and 

 wood-water assays to have a high tolerance for various inorganic salts. 



Examination of the data in Table 3 shows that the compounds produced 

 in the wood by mixture 4 afford almost complete protection to the wood 

 which was treated with 0.72 pound of the salt per cubic foot. The vigorous 

 attack on the untreated blocks is evidence of the severity of the test. Sim- 

 ilarly, the comparable treatment of the wood with 0.8 pound of mixture 1 per 

 cubic foot was very effective in protecting the wood against fungus attack. 

 If the amount of mixture 1 in the wood is doubled, almost perfect protection 

 against decay may be obtained. \\'ood treated with 0.35 pound of mixture 

 3 per cubic foot is protected against Poly poms vaporariits and BTL U-11 l)ut 



