CHAPTER V.— COMPARISON OF THE PROPERTIES OF COMMERCIAL 
COAL-TAR CREOSOTES AND COMMERCIAL WATER-GAS-TAR CREO- 
SOTES. 
It is believed that a short comparison of the properties of com- 
mercial oils will be of value, notwithstanding the fact that they have 
been discussed at some length in the preceding chapters. Table 30 
shows the similarities and dissimilarities of coal-tar creosotes and 
water-gas-tar creosotes. 
Table 30. — Comparison of the properties of commercial coal-tar creosotes and commercial 
v:ater-gas-tar creosotes. 
Coal-tar creosote. 
Water-gas-tar 
creosote. 
Specific gravity of original creosote 
Flash point . . ." 
Burning point 
Distilling range 
Change in specific gravity per degree C 
Sulphonation residue of fractions 275° to 285° C 
Tar-acid content 
Character of hydrocarbon 
Ratio of specific gravity to index of refraction of the fraction 
275° to 2S5 3 C. 
Toxicity 
1.01 and up 1.00 and up. 
70° C. and up i 70° C. and up. 
1 90° C. and up. 
90° C. and up 
170 to 400° C 
0.00078 
to 8 per cent 
Up to 10 per cent 
Chiefly aromatic . 
1.81 
Shown in fig. 37.. 
170 to 400° 
0.00078. 
to 8 per cent. 
None. 
Chiefly aromatic. 
1.56. 
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Fig. 37. — Comparison of the toxicities of coal-tar creosotes and water-gas-tar creosotes. 
The chief difference between these two classes of creosote are a 
total lack of tar acids and bases in the water-gas-tar creosotes, a 
higher general average of the sulphonation residues in water-gas-tar 
creosotes than in coal-tar creosotes, and a lower toxicity. (Fig. 37.) 
The only methods known at the forest products laboratory for 
differentiating between two classes of oils are the determination of 
77 
