160 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



operational losses and through the points representing weight losses. 

 Data from a repetition of these tests is desirable in order to establish 

 the thresholds more definitely from actual weight loss or observational 

 data taken close to the assumed threshold points. At Bell Telephone 

 Laboratories a check series of tests is now under way on cooperative 

 creosotes 6, 7 and 8, domestic oils, and creosotes 9, 10 and 11, British 

 oils; and comparison tests are also being run on creosote BTL-5340 and 

 on 5 per cent pentachlorophenol in the 2105 process oil. The aim has been 

 to treat the blocks to a series of retentions that vary narrowly around 

 the thresholds set by the Madison investigators. 



Across the Threshold 



Fig. 13 is an illustration of representative blocks from the creosote 

 series, line A (creosote BTL-5340) in Fig. 10, just at and below the 

 threshold. Fig. 14 shows the character of the attack by Lenzites trahea on 

 blocks treated with a 4.92 per cent solution of pentachlorophenol in 

 Standard Oil Company of New Jersey's 2105 Process Oil in toluene. The 

 blocks are represented at twice their original linear dimensions. The exact 

 nature of the decay is difficult to show. The experimenter has to learn a 

 system of diagnosis that involves both visual observation and the "feel" 

 of the blocks for distortion and firmness that supplement weight loss data. 

 For example, in Fig. 14, a threshold between 0.20 and 0.25 pound of penta 

 per cubic foot (Blocks C and D) is indicated and this conforms closely to 

 the results with the same penta-petroleum solution at Madison .^^ 



The Significance of the Results of Laboratory Soil-Block Tests on Oil-Type 

 Preservatives 



The main conclusions from this discussion of the results of soil-block 

 tests on weathered creosoted wood conducted at Madison are (a) that 

 in general, under the test conditions, at least 8 and sometimes 9 pounds 

 or more of creosote per cubic foot is a necessary treatment to prevent attack 

 by Lentinus lepideus on %-inch cube blocks of southern pine sapwood; 

 and (b) that a penta petroleum solution is much more effective than 

 creosote against this same organism. As will be emphasized later, this 

 general conclusion about Lentinus lepideus and creosote corresponds with 

 the conclusions to be drawn from the interpretation of results of the 

 small stake tests and from the test of pole-diameter posts in the Gulfport 

 test plot. 



The creosote tested is a better preservative against Lenzites trahea 

 than the penta-petroleum, but the creosote threshold for this organism 



