46 
BULLETIN 1036, U. S. DEPARTMENT OF AGRICULTURE. 
bases. These may easily be added to a water-gas-tar product at 
slight cost, however, and for this reason their presence is not proof 
positive that the creosote in which they are found is of coal-tar origin. 
It was supposed at one time that the color of the fractions was an 
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SPECIFIC GRAVITY AT 60°C 
LOO 1.02 
L06 1.08 
Fig. 27. — Relation between the index of refraction values and the specific gravity of the fractions of creosotes. 
Circles — Coal-tar creosotes. 
Dots— Water-gas-tar creosotes. 
A. Fraction distilling between 255° and 265° C 
B. Fraction distilling betwwen 265° and 275° C. 
C Fraction distilling between 275° and 285° C. 
D. Fraction distilling between 285° and 295° C. 
indication of a mixture of water-gas-tar oils with coal-tar creosotes. 
This investigation has shown that the supposed characteristic green 
color of certain of the fractions is common to all creosotes or oils 
having a high sulphonation residue, and that this color, therefore, 
does not indicate a mixture of the two kinds of oil. 
