EVALUATION OF WOOD PRESERVATIVES 



159 



lives; and the mixture of creosote and penta solution is somewhat bet- 

 ter than the penta solution alone, although the difference is not great. 



The results obtained in testing the different creosotes represented in 

 Fig. 11 are similar in general character for the four domestic oils, but 

 oil No. 11, the mixture of British vertical retort tar creosote and British 

 coke oven tar creosote, appears to behave differently. The thresholds for 

 all of these creosotes, as determined by the Madison investigators, are 

 shown in Table XXXV. The figures in this table correspond very closely 

 to thresholds determined by visual observation of the test blocks. 



Check Tests at the Murray Hill Laboratories 



It will be noted that in Fig. 11 the points used for locating the graphs 

 are rather far apart in the general region of the estimated thresholds. 

 The values shown in Table XXXV were obtained at Madison by the 

 intersection of regression lines drawn through the points representing 



Table XXXV — Summary and Interpretation of 

 Soil-Block Tests 

 Weathered, creosoted southern pine sap wood blocks; creosote losses; amounts 

 and gross characteristics of residual oils at threshold retentions for Lentinus 



* Creosotes 1, 2, 3, 6, 7, 8, 9, 10 and 11 are those in use in the Cooperative 

 Creosote Tests (see Bibliography, References 12 and 39. Oils 9a and 10a are 

 samples from the same lots as numbers 9 and 10. (See Bibliograph>', Reference 

 36.) For oils Ml and M2 see Bibliographj^, References 37 and 38. Creosote 5340 

 is shown in Table II. 



