CHAPTER Vn. A THEORY OF THE MECHANISM OF THE PROTECTION 

 OF WOOD BY OIL SOLUTIONS. 



The author has recently proposed a theory of the mechanism of the 

 protection of wood by preservatives, which is based on the two ideas, 

 first, that any material in order to be toxic must be soluble in the 

 body fluids of the organism it is intended to inhibit, and second, that, 

 as the body fluids of timber-destroying organisms are chiefly water, 

 the material must be soluble in water, at least sufficiently so to pro- 

 duce a solution of lethal concentration. For the purposes of this 

 theory all the constituents of creosote oil may be divided into two 

 classes. The first class comprises those materials that are sufficiently 

 soluble in water to render them poisonous. These may be called 

 toxic oils. They may be hydrocarbons, such as benzene, toluene, 

 xylene, naphthalene, etc.; or tar acids, such as cresols, naphtols, etc.; 

 or tar bases, such as quinoline, isoquinoline, etc.; or a combination 

 of all three. Their chief characteristic is that they are sufiiciently 

 soluble in water to render their water solution capable of killing the 

 wood-destrojdng organism. The second class of compoimds com- 

 prises those that are not sufficiently soluble to render their water 

 solutions toxic. This class of oils may be composed of the same types 

 of compounds as those previously enumerated, and these oils differ 

 from those of the other class only in their relative solubility. They 

 may even be soluble to a slight extent, and in all probability they 

 are. This class may be called nontoxic oils. 



The toxic oils are completely soluble in the nontoxic oils and are 

 partially soluble in water. When creosote comes in contact with 

 water, these toxic oils will so divide themselves between the water 

 and the nontoxic oils that their concentrations in water and in the 

 nontoxic oil will be nearly in proportion to their solubility in the two 

 mediums. This is known as the solubility partition. For the sake of 

 argument, a toxic oil may be assumed which is fifty times as soluble 

 in the nontoxic oil as it is in water, and it may be assumed that a 10 

 per cent solution of this toxic oil is used in the nontoxic oil. When 

 such a solution comes in contact with an equal volume of water, the 

 concentration of the water solution will be 0.2 per cent. If now the 

 toxic limit of this water solution is only 0.05 per cent, then the water 

 solution will be four times as toxic as is necessary to kill. It may be 

 assumed that tliis water is now withdrawn and an equal amount 

 added, which in turn takes up its proportion of toxic oil and is ren- 

 dered poisonous. This change of water can take place seventy times 

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