472 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



surface area only of the flat blocks. The losses are interpreted in general 

 to mean that the exposure conditions were not as severe as those in the 

 Rhodes^^ weathering wheel tests, and in line with his outdoor tests. 



The results of recent determination at Bell Telephone Laboratories of 

 creosote losses from %-inch cube blocks, by toluene extraction, are shown 

 in Table XXX. The blocks were divided into thirds before extraction 

 (Fig. 30) and the respective parts were further divided and then pooled 

 in the extractor. 



The blocks in each group of twenty were selected to represent the 

 whole gradient of treatments with an average treatment retention for 

 each group of 6.05 pounds per cubic foot. The average density of the 

 blocks, oven-dry weight and volume basis, was the same for each group, 

 namely 0.56. The oil used was cooperative creosote No. 11, a 50/50 blend 

 of British vertical retort tar creosote and British coke oven tar creo- 



sote," 



diluted as usual with toluene. The exposure period outdoors 



was sixty days at the Chester Field Station between January 4 and 

 March 3, 1952, plus several days exposure on a bench in a steam heated 

 laboratory both before and after the outdoor period. The average loss of 

 40.3 per cent is considered to be in line with losses for the same creosote 

 in the Madison tests, considering the factor of the winter chmate at 

 Chester. 



The distribution of the residual creosote in the test blocks as sho^vn 

 by the averages reported may be considered to be remarkably uniform. 

 The differences in these averages are not regarded as statistically signifi- 

 cant. Further discussion of losses from weathered blocks will be resumed 

 in later paragraphs. 



Table XXX — Creosote Losses from Loblolly-Shortleaf 

 Southern Pine Sapwood Blocks, and lb/cu ft Remaining 

 By toluene extraction; outdoor winter weathering tests — BTL (Snoke and 

 MacAllister) data. 



Average lb/cu ft of creosote remaining; 



in outer thirds 



in middle thirds 



in whole blocks 



Average loss of creosote; 2.44 lb/cu ft, or 40.3 per cent. 



3.68 

 3.56 

 3.61 



♦ ^-inch cubes. See cutting diagram in Fig. 30. 



