172 



As already noted here there are sHght differences in composition in the oil recov- 

 ered from different layers of the treated wood. This condition, however, is apparently 

 one which arises after treatment when an equilibrium rate of loss has been established, 

 since studies of successive layers in recently treated piles indicate that creosote pene- 

 trates the wood in an unaltered condition. That is, with straight or whole run 

 creosotes, there is no tendency toward filtration of the heavier constituents in the 

 outer layers of wood. 



Fixation of Creosote Constituents 



It has been suggested that the low boiling fractions of creosote are not entirely 

 lost, but that part of them polymerize or condense to higher boiling constituents, 

 thus becoming more or less permanently fixed in the wood. Some of our earlier results 

 seemed to indicate that this was the case. However, very careful further study of this 

 point gave only negative results. Although all changes in composition found were in 

 the direction to indicate polymerization, they were too small to be of any significance. 



The idea has also been put forward that certain creosote constituents are fixed 

 in the wood by an actual combination with the wood. Any such combination must 

 be very loose, since we have shown that it is possible to recover creosote completely 

 by a benzene extraction. Furthermore, careful analyses of the wood itself before 

 treatment and after removal of the creosote, show no significant differences. Table 23 

 gives the results of these analyses. 



TABLE 23 



AN.'XLYSIS OF WOOD SUBSTANCE OF DOUGLAS FIR SAPLING BEFORE AND AFTER 



TREATMENT WITH CREOSOTE 



*Benzene Alcohol 



soluble soluble Cellulose Lignins Mannan 



extract extract 



Before Treatment .. . 0.20% 3.28% 56.66% 28.25% 7.39% 



After Extraction 0.21% 3.77% 55.22% 28.48% 



*A11 results calculated to 4.0"^^ moisture content. 



/o 



INORGANIC TREATMENTS 



For many years various inorganic salts have been used in the preservation of 

 wood. However, the only ones which have attained at all general use are zinc chloride, 

 copper sulphate, and mercuric chloride. Even these have not been used to any great 

 extent under high moisture conditions, on account of their large solubility and con- 

 sequently rapid leaching from the wood. 



The value of any treatment depends upon two factors, the immediate effective- 

 ness of the protection afforded, and the permanence of the protection. Obviously, 

 even though such substances as those mentioned might afford protection for a short 

 time, they have no value for the permanent preservation of marine piling, since they 

 would too soon be lost from the wood. 



It is readily seen that the high moisture conditions to which marine piling is 

 subjected make the preservative use of inorganic salts very difficult. Either they must 

 be left in the wood in some very slightly soluble form, in which case their preservative 

 value is presumably cut down, or else leaching must by some means be prevented. 



The only readily apparent method for leaving inorganic salts in the wood in a 

 soluble form and still having permanent protection is by the use of oil emulsions. All 

 available petroleum oils are lighter than water: The formation in these oils of stable 

 emulsions of solutions much hea^•ier than water is a matter of some difiicultv. The 



