EVALUATION OF WOOD PRESERVATIVES 



431 



Depreciation Curves for Y^ Inch Stakes 



Under the conditions at Gulfport the depreciation curves for the cre- 

 osotes — particularly the low residue oils — show an increased down- 

 ward pitch at the 6th to 7th year of exposure. The relative proportion 

 of the stakes rated respectively at 10, 9, 7, 4 and at the 6- and 7-year 

 inspections, are shown by number and per cent in Table XI. The change 

 within the one year interval is particularly striking in the 10 and 9 

 columns. The rating and the distribution of retentions of creosote 5283, 

 empty-cell treatment, at 6 and 7 years, respectively, are shown in Figs. 



100 



80 



O 70 



cc 



HI 

 Q. 



60 



50 



40 



30 



20 



:!:!.-: 



tU 



:! 



illl I 



•-•-• — • — • — • 



EACH DOT REPRESENTS 

 ONE SPECIMEN 



3456 789 10 



TREATMENT RETENTION IN POUNDS PER CUBIC FOOT 



Fig. 15 — Distribution of ratings in relation to fetention by weight at treatment; 

 creosote No. 5283, ^-inch southern pine sapwood stakes; 1941 series, empty-cell 

 treatment; six years exposure; Gulfport test plot. See text and companion Figs. 

 16, 17 and 18. 



