64 



BULLETIN 1036, U, S. DEPARTMEjS^T OF AGRICULTURE. 



Recently Bateman and Town (26) have shown that the loss of 

 creosote by weight because of evaporation in laboratory open-tank 

 treatments is in direct proportion to the area of the surface of the 

 oil, and is also dependent upon the volatility of the creosote. They 

 give the equation log i = 0.0165 F— 0.347 as the daily loss per square 

 foot of exposed surface, when the temperature of the bath is 195° 

 F. In this equation log L is the logarithm of the loss and V is the 

 percentage of creosote distilling below 270° C. The constants 0.0165 

 and 0.347 will vary if any of the conditions are used except those 

 under Avhich the experiment was carried out. Figure 32 gives a 

 curve of the above equation, with the experimental data plotted 

 upon it. 



f 



/.OSS ~ /^ot//icfs yoe/- sfi/are /oo^ /jer i^a/ 



Fig. 32. — Relation between the volatility and the loss hy evaporation of 

 creosotes from open tanks. 



Calculations show that it is very likelj^ there is a mathematical 

 relation between the rate of loss of creosote from treated wood and 

 the amount and character of the creosote injected. The general 

 form of the equation, as obtained from preliminary calculations, is 



"^ 



1^ 



B-Y 



= X 



where -fiT is a constant for the location, A is the weight of creosote 

 injected per cubic foot of wood, B the percentage of creosote dis- 

 tilling below 270° C, Y the loss by evaporation, and X the time 

 required. 



Figure 33 gives two curves m which the above equation has been 

 used on two different creosoted sticks which had different grades of 

 creosotes and different absorptions per cubic foot. In one curve the 

 amount of oil distilling below 270° C. was 92 per cent, in the other 

 curve 49 per cent. The amounts of oil injected per cubic foot were 



