EVALUATION OF WOOD PRESERVATIVES 



149 



These same values for these three charges, 19, 20 and 21, and similar 

 values for charges 71-76, inclusive, are incorporated along with average 

 and range of retention data in Table V, and with statistical data for 

 regression lines in Table VI. The data serve to illustrate the degree of 

 variability in treatment results that may occur when random blocks are 

 used. The best indices of these variations are in the columns showing 



Table V — Retention Data for Full-Cell Treatment 

 Soil block tests; average and range of preservative retention, by charges, at 

 treatment. 



Table VI — Full-Cell Treatment 



Soil-block tests with (a) penta-petroleum creosote, and with (b) creosote, in 

 toluene; relation of variable block density to absorption of treating solution. 



* <r = standard deviation. 



t c.v. = coefficient of variability, per cent. 



