EVALUATION OF WOOD PRESERVATIVES 461 



higher quantities of respective creosote fractions were required to kill 

 Fomes annosus in the pulp cultures than in Petri dish agar cultures. 

 They concluded from their experiments that "no one compound in coal- 

 tar creosote is primarily responsible for its preservative power. . . . The 

 fractions from water-gas tar oil are much less effective as preservatives 

 than are those from coal-tar creosote oil. The chlorine derivatives of 

 phenols and creosote and of naphthalene are more toxic to fungi than 

 are the compounds from which they are obtained." 



In 1933 Flerov and Popov^^ tested fractions of two creosotes by their 

 soil-block method and compared the results Avith tests of the fractions 

 emulsified in agar, following American Petri dish procedure in general. 

 They found (English translation by Hildegard Kipp, Forest Products 

 Laboratory) : 



"On wood the toxicity of the heavy fractions is considerably higher 

 (compared to that of the lower fractions) and the most toxic fractions 

 are those from 315 to 375°C. ... In tests on wood, in addition to the 

 preservative effect, the effect of the evaporation factor, which is of great 

 importance with oily preservatives, is determined T\dth (more or less) 

 accuracy." 



In 1951 Finholt^^ revives the use of emulsion of the creosote fractions 

 in the old Petri dish or flask method, like history repeating itself. The 

 reader can be excused if he senses a degree of confusion. 



Creosote Losses 



Baechler's 1949 paper^ on the toxicity of oils before and after aging 

 would be a fitting introduction to this section. The first task is to con- 

 dense into simple statements or tables some of the available data on 

 creosote losses from treated wood. 



Curtin^^ cites Bond on the latter's experimental determination in 

 1910-11 of creosote losses from thoroughly air-seasoned red oak and 

 maple railroad ties with approximately the same moisture content. Bond 

 reports that : 



1. Full cell treated red oak in 200 days between November 1910, and 

 June 1911, lost 19.0 per cent; and 



2. Similar empty cell treated ties lost 52.7 per cent; and 



3. Full cell treated maple ties in 105 days from March to June 1911, 

 lost 13.4 P^f cen^; and 



4. Similar empty cell treated ties lost 23.0 per cent of the creosote 

 absorbed at treatment. 



The losses were determined by weight. He shows that the losses were 



