484 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



creosotes with respect to the indicated threshold amounts distilling helow 

 35 5° C. Statistically, the figures in Table XXXV Col. 11, are not signi- 

 ficantly different. Slight changes in estimating the thresholds would con- 

 ceivably bring them all to approximately the same level. In any given 

 set of experiments the level would also vary with the duration (and 

 types) of a different weathering cycle. 



It will be recognized that no attempt has been made to separate or 

 define the gross components of the fraction remaining below 355°C. 

 This calls for more study, and for the development of refined methods 

 of extraction and assay by weight and by distillation. Also, no attempt 

 has been made to interpret the value or significance of the residue above 

 355°C, either because of its possible retardation of the evaporation of 

 lower fractions, or because of some potential mechanical blocking effect. 

 The whole interpretation is based on the simple division of the creosotes 

 into two parts, the part distilling below 355°C and the part distilling 

 above 355 °C. Refinement will depend upon better future experimental 

 evidence. 



As an illustration of the application of the hypotheses discussed in 

 the preceding paragraphs, one may reexamine the data from the weath- 

 ering wheel experiments.^^ Rhodes, Roche and Gillander used one creo- 

 sote retention only in their weathering wheel experiments, namely 16.7 

 pounds per cubic foot. In commenting on their work C. S. Reeve^' ^' ^^~^^ 

 noted Rhodes' emphasis on "the fact that toxicity without permanence 

 is just as worthless as permanence without toxicity". Reeve and his 

 colleagues carried out somewhat similar weathering experiments using 

 slabs of wood about J^ inch thick, exposing the treated pieces to some- 

 what lower temperatures than those in the Rhodes' experiments and 

 ''following a procedure with circulated air, and heat, and water". The 

 plan of the experiments called for the conduct of "weathering cycles 

 with reduced increments of various oils in order to get down finally to 

 a percent of impregnation right at the end of a weathering cycle which 

 would actually yield a rotting specimen of Lentinus lepideus^'. The work 

 had not progressed far enough to accomplish this end, but Reeve says 



"The results . . . are in very close corroboration of what Mr. Rhodes 

 has found. In other words, our loss curves with different oils running 

 from relatively low residues to relatively high residues, have been almost 

 parallel, I believe, with the loss curves which he has shown ..." 



Rhodes et al used essentially an agar-block method for testing their 

 weathered blocks against Lentinus lepideus, Mad. 534, the same strain 

 as that used in the Madison tests. The residual creosotes in the blocks 

 treated with Oil I and Oil II (Table XXVI) are calculated to have been 



