72 



BLILLETIX ]036, V. S. DEPAETMEXT OF AGRICrXTUBE. 



shows the percentage distilling from each fraction within the limits 

 of the other fractions. 



Table 27. — Relative composition of fractions of coal-tar creosotes when redistilled hy 



Eempel flask {30). 



Fraction 

 No. 



Amount distilling within the limits of— 



Fraction 

 1. 



Fraction 1 Fraction 

 2. i 3. 



Fraction 

 4. 



Fraction 

 5. 



1 

 2 

 3 



4 

 5 



Per cent. 

 63 

 10 



PcT cent. Per cent. 



37 1 



i 

 Per cent. Per cent. 



72 I 26 



22 1 52 



1 ! 22 



2 

 20 





6 





31 46 





3 



21 76 1 











A more refined analysis would, of course, increase the distillation 

 range. Huntley has sho'\\Ti that on the redistillation of fraction -i 

 the following initial boiling points were obtained, the initial boiling 

 point at the still having been 295° C. 



Initial boiling point of second distillation 270 



Initial boiling point of third distillation 210 



Initial boiling point of fourth distillation, 140 



Initial boiling point of fifth distillation 137 



In other words, although the initial boiling point at the still was 

 295° C, this fraction contained a small amount of material boiling 

 below 200° C. This amount was found to contain approximately 

 20 per cent of tar acids, and the amount boiling from 200° to 235° C, 

 contained considerable quantities of tar bases. Both of these are 

 very toxic materials and in the pure state are soluble in water; when 

 mixed with oils in which they are soluble their extraction with water 

 would take a very long time. 



The two factors that govern the preserving value of any wood 

 preservative are permanence and toxicity, but these two factors 

 seem to be diametrically opposite. The relation between them is 

 shown in fio:ure 34. 





, 















'^~ 







' 











^^ 



^^ 











^^ 



^^ 



~~" 





5^00 





















































I 





















































S 





















































Z 





















































-J 

 g 40 





















































o 





















































111 

 u 20 



w 





















































V 





















































(K 



V- 























< 



OAL 



TA 



( CI 



STI 



.LA 



ES 













~ 

















1 



F" 







Pi 



2 



:Rcf 





RE 



QUI 



4E0 



3 

 TO 





 KIL 



L 







4 













4> 



Fig. 34.— R31ation between the volatilitT and toxicity of coal-tar creosotes. 



