EVALUATION OF WOOD PRESERVATIVES 



445 



Q. 



50 



I I SOUND 



|:B>l::M:i SLIGHT DECAY 

 ^^^ MEDIUM DECAY 



POSTS GROUPED IN 



2 POUND RETENTION 



INCREMENTS 



12345 6789 10 II 



RETENTION BY EXTRACTION IN POUNDS PER CUBIC FOOT AT TREATMENT 



Fig. 28 — The relation of creosote retention in Ib/cu ft at treatment by toluene 

 extraction, and the rated condition of pole -diameter test posts, by retention 

 groups; 1950 inspection; Gulf port test plot. See text and Table XVI. 



eleven groups are shown graphically in Fig. 27. The relation of retention 

 by extraction at the time of treatment to the sound, decaying and failed 

 specimens is clearly evident. All of the failures and the very great ma- 

 jority of the remaining decaying poles are below the 7-pound retention 

 hne. Only two cases of medium decay occur above the 7.5 pound line. It 

 should be borne in mind particularly at this point that these retention 

 levels represent the retentions found by extraction in the whole cross 

 sections of the posts as soon as practicable after the posts were treated. 

 The significance of these over-all retentions and of the calculated reten- 

 tions in the outer one-inch layer of the posts will be discussed later. 

 Since the data were calculated in terms of oven-dry weight and volume 

 of the extracted wood the values may be a little high. 



For Groups 5 to 10 inclusive data are available on the retention in 

 zones, that is, in the outer quarter inch, the next quarter inch, the next 

 half inch, the next one inch, and the remainder of the treated sapwood. 

 These data were obtained by appropriate cutting of the samples into 

 zones and pooling for extraction the parts that came from the same zones, 



