314 Forestry Quarterly 



ride and with corrosive sublimate, and of the newer methods 

 that with sodium fluoride, which forms the chief ingredient of 

 the Wohlmann sah mixture. 



From the standpoint of economy, the cost of treatment is the 

 deciding factor, next to the effectiveness. It is, of course, im- 

 possible to give in an order which will prove true for all cases 

 the economic value of the several methods of treatment. Of 

 the methods involving the use of salt solutions it can at least be 

 said that in the United States on the basis of one cubic foot of 

 wood and one year's duration (annual charge?) the treatment 

 with copper sulphate comes highest and zinc chloride somewhat 

 cheaper, the treatment with corrosive sublimate and with sodium 

 fluoride being, in comparison, the most advantageous. It has, 

 indeed, been said that the conditions seem to vary in individual 

 mines and that it is not at all necessary, therefore, to use the 

 most effective agent everywhere. But it must be remembered 

 that there never occurs one species only of wood-destroying fun- 

 gus in a mine. We always find a great number of the most di- 

 verse kinds together ; wherefore we must always direct our efforts 

 against those which require the most powerful combative meas- 

 ures. The materials introduced into the wood must retain their 

 effectiveness for a long time. They must therefore be neither too 

 quickly changed into less effective substances nor too readily 

 evaporated from the wood nor washed out by seepage waters. 

 There must also be taken into consideration a chemical change 

 by the action of materials contained in the seepage waters. As 

 far as the salts used in mining are concerned, only the last two 

 points need be seriously considered. As a matter of fact, the 

 danger of washing out has always been greatly exaggerated, and 

 it is therefore especially gratifying to find Dr. Thomann, chief 

 chemist for Guido Rutgers in Vienna, on page 33 of his pamphlet 

 Leitimgsmaste (Poles for Electric Wires), writing with reference 

 to zinc chloride, in the case of which, as is known, washing out 

 is most feared : "Zinc chloride can, because of its solubility be 

 dissolved out, but in spite of this fact, it exhibits results which are 

 well worthy of consideration before the fear of washing out be 

 too greatly over-emphasized. Its low price maintains for it even 

 up to the present time a moderately extensive application in Aus- 

 tria as a material in which to dip railroad ties." 



A changing of a salt into a less effective substance has fre- 



