458 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



General Considerations; Creosote Fractions 



Before presenting definite evidence of creosote losses this seems as 

 good a place as any to refer briefly to investigations that have been aimed 

 at discovering what components, volatile or relatively stable, give creo- 

 sotes their properties of toxicity and permanence. Three articles by 

 Martin,^^ Rhodes^^ and Mayfield^^ are the latest American papers cover- 

 ing the general subject, the two former dealing with the technology of 

 hydrocarbons and creosotes and creosote production and the latter re- 

 viewing the results of tests of whole creosotes and creosote fractions. 



Teesdale's short report^^^ in 1911 is one of the earlier records in this 

 country of experiments aimed at determining the loss of creosote frac- 

 tions from treated wood. He used a creosote with 49 per cent distilling 

 below 250°C and a residue above 320°C of 28 per cent, which would have 

 been about 20 per cent at 355°C. This oil was fractionated into 5 parts, 

 I, to 205°C; II, 205-250°C; III, 250-295°C; IV, 295-320°C; and the 

 residue above 320°C. These five fractions and a sample of creosote with a 

 similar distillation range were used to treat air-seasoned pieces of Pinus 

 taeda, mostly sapwood, cut 2 feet long from 5 to 6-inch diameter peeled 

 posts. The retentions were about 18 pounds for the numbered fractions, 

 15 pounds for the residue, and 21 pounds for the whole creosote. 



The treated pieces were open-piled in the laboratory for tw^o months, 

 with temperatures running from 60 to 80°F. At the end of that period 

 the per cent losses of the five fractions and the creosote were respectively 

 34.7, 21.3, 15.9, 6.2, 4.0 and 5.4. The results were in line with expecta- 

 tions. The test period was short, and there were no outdoor weathering 

 factors. Teesdale notes that the loss of the whole creosote was about the 

 same as the losses in the two higher fractions. III and IV; and that a 

 proportionately composited sample of the five fractions lost at the rate 

 of fraction III, the total at the end of the two-month period being 15.8 

 per cent or about three times as great as for the whole creosote. 



Loseby and Krogh^^ reported in 1944 on outdoor weathering tests of 

 creosoted wood blocks ; and they compared the weight losses in the blocks 

 with evaporation losses from open Petri dishes. The creosote used was a 

 relatively low residue oil produced at Pretoria. The residue above 355°C 

 was 19.95 per cent, the specific gravity at 38/20°C was 1.088, and the 

 amount distilling to 235°C was only 4 per cent. The test blocks were 

 planed pieces of light weight Pinus insignis measuring 6 x 13^^ x IJ^ 

 inches. The per cent moisture at the time of treatment was 10.3 per cent. 



The creosote was fractionated into four parts; Fraction I, up to 270°C; 

 Fraction II, 270-315°C; Fraction III, 315-355°C; and. Fraction IV, the 



