48 BULLETIlSr 1036, U. S. DEPAETMENT 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. Compomids of this type may be termed cychc 

 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 



