72 
BULLETIN 1036, IT. S. DEPARTMENT OF AGRICULTURE. 
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 by 
Hempel flask (30). 
Fraction 
No. 
Amount distilling within the limits of— 
Fraction Fraction 
1. 2. 
Fraction 
3. 
Fraction 
4. 
Fraction 
5. 
1 
2 
3 
i 
5 
Per cent. Per cent. 
63 37 
10 72 
22 
Per cent. 
Per cent. Per cent. 
26 
52 
22 
3 
2 
20 
6 
1 
31 46 
21 76 

A more refined analysis would, of course, increase the distillation 
range. Huntley has shown that on the redistillation of fraction 4 
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 figure 34. 
K>0. 
o 
1 
15 00 
* °° 
o 
m 
z 
» 40 
s 
z 
u 
O 20 
X 
III 
V 
V. 
Sr- 
* 
C 
0AL 
TA 
R Dl 
STI 
lla- 
rEs 
, 

1 

PI 
2 
:rce 

NT 
RE 
aui 
*ED 
3 
TO 

KIL 
L 
4 

5o 
Fig. 34.— R31ation between the volatility and toxicity of coal-tar creosotes. 
