EVALUATION OF WOOD PRESERVATIVES 



Creosote Losses from Impregnated Filter Paper 



473 



There have been numerous criticisms of the use of creosote loss figures 

 obtained by evaporation from open dishes in any consideration of creo- 



108 



sote permanence. The use of the losses reported in this section may 

 be criticized in a similar manner, but they represent extreme acceleration 

 and they seem to have a bearing on the interpretation of any weathering 



Fig. 30 — Diagram of cutting plan for dividing a weathered creosoted block into 

 three approximately equal parts for determination of residual creosote by toluene 

 extraction. 



tests in which evaporation plays the major part. Some years ago the late 

 Heinrich T. Boving of Bell Telephone Laboratories, ran an extensive 

 series of evaporation experiments on eight so-called Fulweiler creosotes. 

 He used impregnated strips of filter paper, hung on quartz springs in 

 protecting glass apparatus and exposed to a constant flow of air with 

 no turbulence, and under constant temperature and humidity. His ex- 

 periments were performed with great care. Repetitions gave excellent 

 agreement. A condensation of his loss figures, rounded off to whole num- 

 bers, for seven- and fourteen-day exposure periods, are shown in Table 

 XXXI. Let it be stated unequivocally at this point that it is recognized 

 that there are important physical differences in the wood fiber combina- 

 tions represented by filter paper, wood blocks, small round saplings, 

 posts and poles ; but the quantitative loss data seem to fall sooner or later 

 into a similar pattern for all these test media, under the various condi- 



