EVALUATION OF WOOD PRESERVATIVES 469 



in Table XXV. The loss figures are averages for all the creosotes used. 

 It will be noted that there is a large variation in the treatment retention 

 groups and that the losses were more rapid and definitely higher for the 

 lower retention empty-cell specimens. Preliminary estimates from data 

 on creosoted J^-inch square stakes at Gulf port indicate losses of about 

 the same order of magnitude, with the trend in the direction of rela- 

 tively higher figures than those for the round saplings. This is in line 

 with expectation because of the use of the toluene diluent and the practice 

 of controlling the treatments to secure lower than threshold retentions in 

 both full-cell and empty-cell treatments. 



Creosote Losses from Treated Blocks 



E. 0. Rhodes and his colleagues have published two excellent pa- 

 pers^°' ^^ that are most significant in a discussion of creosote losses from 

 treated wood blocks. They used two creosotes, I and II, the analyses of 

 which are shown in Table XXVI. Southern pine sap wood blocks meas- 

 uring 0.5 X 0.5 X 3.0 inches, with the long axis in the direction of the 

 grain, were treated and exposed on a weathering wheel in the laboratory, 

 and also out of doors. The laboratory test specimens were treated to a 

 retention of 16.7 pounds per cubic foot by soaking the blocks, heated to 

 105°C, in creosote at 100°C, in a sealed container. The creosote cooled 

 during a five-hour soaking period to 40-50°C. The authors felt that the 

 retention of about 16.5 pounds would facilitate extraction recovery of 

 enough oil for analysis, and that ''the treated portion of a tie or pole 

 probably contains about this amount of oil." Bell Telephone Labora- 

 tories' experience has shown (Fig. 29) that the retention in the com- 

 mercially treated 8-pound post averages only about 12 pounds per cubic 

 foot in the outer J^ inch of wood and that the retention drops off rapidly 

 in the wood farther beneath the surface. The Rhodes blocks, therefore, 

 must be regarded as heavily treated. 



Losses of creosote were determined by ether extraction, and the change 

 in character of the preservative was determined by distillation of the 

 extracted oil. Corrections were made for resin extracted with the creo- 

 sote. The losses of creosote from the test blocks on the weathering wheel 

 are shown in condensed form in Table XXVII. 



The authors report creosote loss from blocks treated to a 15.0-pound 

 retention and exposed outdoors during the winter as 44.4 per cent; and 

 similar blocks treated to a 16.5-pound retention lost 47.1 per cent in a 

 nine-week exposure period during the summer. The results of the experi- 

 ments were taken to mean that the losses were of about the same charac- 

 ter in the outdoor winter and summer exposure tests, and that the blocks 



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