6 BULLETIN 1036, U. S. DEPARTMENT OF AGRICULTURE. 
obtained from coal tar, and, in this respect it means the mixture of 
phenoloids known to the wood preserver as tar acids. 
Creosote oil is the term correctly applied to that portion of wood 
tar or coal tar from which creosote may be obtained by extraction 
with caustic soda and a subsequent neutralization of the aqueous 
liquors with mineral acids. 
Common usage in the wood-preserving industry has led to the 
disuse of the word ''oil" and to the application of the term " creosote" 
to the mother liquor, or crude oil, from which true creosote may be 
obtained. Because of the similarity in other respects between the 
oil obtained from coal tar — that is, the true creosote oil — and that 
obtained from water-gas tar, the term " creosote oil" has been applied 
to oils containing no phenoloids whatsoever. In this publication, 
the term "creosote" is applied only to a pure product obtained by 
the distillation of tars, and will be restricted to the oils obtained from 
high-temperature coal and oil tars and to wood tars. They will be 
further defined by the use of some qualifying word or phrase such as 
coal-tar creosote or water-gas tar creosote. All the distilled oils 
(except patented or proprietary articles) will be called oils or dis- 
tillates, and suitably designated to show their derivation. Mixtures 
of distilled oils with their mother liquor or with the mother liquor 
from other distilled oils will be termed tar solutions. More specifi- 
cally, these terms are defined as follows: 
Coal-tar creosote is defined as any and all distillate oils boiling 
between 200° and 400° C, which are obtained from high-temperature 
coal tars by distillation only. The addition or admixture of tars 
from any mixture or source, either refined, filtered, or crude, is not 
permitted under this definition. 
Water-gas-tar creosote is defined as any and all distillate oils boiling 
between 200° and 400° C, which are obtained from water-gas tar 
or other high-temperature oil tars by distillation only. Admixture 
of other materials than those stated above changes the nomen- 
clature. 
Wood-tar creosote is a distillate oil obtained from wood tar. It has 
a specific gravity greater than 1 and distills principally above 170° 
C. at atmospheric pressure. 
Shale oil is the oil obtained from the distillation of shale tar. 
Mond oil is the oil from the distillation of Mond-producer tar. 
Petroleum oil is used in the ordinary meaning, but also includes 
the oil from low-temperature oil tars. 
Retort oil is the distillate above 200° C, obtained from low- 
temperature coal tars produced in the gas retort. It is similar in 
composition to Mond oil. 
