48 BULLETIN 1036, U. S. DEPARTMENT OF AGRICULTURE. 
lene fraction of creosote oil, is composed chiefly of this compound, 
mixed with sufficient quantities of other compounds to render it 
liquid at room temperature. 
The highest fractions of creosote are composed chiefly of com- 
pounds of the fluorene and anthracene series. The compounds of 
these series boil from 270° C. to above 400° C. The members of 
these series that are found in the largest quantity in creosote oil are 
phenanthrene, anthracene, and fluorene. All of these will crystal- 
lize from the creosote oil on standing. The heavy solid matter crys- 
tallizing from foreign oils is a mixture of these three compounds with 
other hydrocarbons and bases. Anthracene is used to a considerable 
extent in the manufacture of dyes; some of the foreign creosotes may 
therefore have been robbed of this constituent. 
Besides the hydrocarbons, which constitute by far the greater 
proportion of creosotes, there are a number of compounds containing 
oxygen which are collectively known as tar acids. These are not 
true acids in a chemical sense, but are phenols. They have some of 
the properties that are usually ascribed to acids, but also some of 
the properties that are characteristic of the alcohols. They are 
characterized by being extremely toxic to bacteria and fungi as well 
as to higher organisms. The higher homologues of phenol — the 
cresols and the xylenols — which are found in creosote, are as destruc- 
tive as phenol to living organisms, if not more so. As the phenols, 
cresols, and xylenols may be considered the alcohols or tar acids of 
benzene, toluene, and xylene, so also in creosote are found com- 
pounds of an alcoholic nature known as naphthols, which are derived 
from the members of the naphthalene series. These, too, are used 
in medicine, as bactericides and antiseptics. At the present time 
the total amount of tar acids in creosote oil does not exceed 10 per 
cent and is usually less than 5 per cent. 
Coal-tar creosotes contain also a number of compounds having 
nitrogen as one of their component parts. These are collectively 
known in this connection as tar bases. Just as it may be considered 
that the phenols are obtained from the hydrocarbons by the addition 
of an alcohol group, so it may be considered that one type of these 
tar bases is derived from the same hydrocarbons by the addition of 
an ammonia group. Aniline and the toluidenes are examples of this 
type of tar base derived from benzene and toluene, respectively. In 
general, however, this type of nitrogen compound is so low boiling 
that it is not found to any great extent in coal-tar creosotes. Another 
type of nitrogen compound contains this element in a much more 
stable condition. Compounds of this type may be termed cyclic 
nitrogen compounds, and are represented in coal-tar creosote by 
the pyridenes, the quinolines, and the acridines. These compounds 
bear the same relation to one another as benzene, naphthalene, and 
