PART in. PROPERTIES OF CREOSOTES. 
CHAPTER I. COMPOSITION AND CHEMICAL PROPERTIES OF COAL-TAR 
CREOSOTE. 
COMPOSITION OF COAL-TAR CREOSOTES. 
The heavy oils of coal tar that are usually known to the trade as 
creosote oil and carbolineums are in general composed of compounds 
of the aromatic series and are usually somewhat complex in their 
chemical structure. The hydrocarbons, that is, those compounds 
containing only carbon and hydrogen, are represented by members 
of at least six subdivisions of the aromatic series. 
The simplest of these is the benzene series, in which fall such com- 
pounds as benzene, toluene, and xylene. These are mainly low- 
boiling compounds — boiling below 200° C. — and are lighter than 
water, but, on account of the difficulty in separating these com- 
pounds from members of other series having higher boiling points, 
they may be found in the oils that are heavier than water. 1 
The next higher series is probably the indenes. These also are 
low boiling, that is, they boil below 200° C, but in all probability 
they are found in coal-tar creosote. 
The naphthalenes, of which naphthalene itself is the most impor- 
tant member so far as creosote oil is concerned, have boiling points 
between 200° and 270° C. when they are in the pure state. Some of 
this series are liquid at room temperature, but naphthalene, the 
parent of the series, is solid at ordinary temperatures, and, if it is 
pure, melts at 80° C. and boils at 218° C. Naphthalene may be 
present in almost any proportion in commercial oils. Samples of 
creosote, examined by the author, have contained as high as 75 per 
cent of oil boiling below 225° C, of which fully 75 per cent was 
naphthalene. On the other hand, oils such as the carbolineums con- 
tain practically no naphthalene. Acenaphthene might be termed a 
derivative of naphthalene. It has a somewhat higher boiling point, 
namely, 275° C. In the pure state this compound is a beautifully 
crystallized white material, melting at 95° C. It is characterized by 
its great solubility in hydrocarbon oils, especially those found in 
creosote; hence it rarely, if ever, crystallizes out from the mother 
liquor. Experiments at the Forest Products Laboratory seem to 
indicate that the golden yellow oil, which occurs above the naphtha- 
1 Huntley, in a master's thesis offered at the "University of Wisconsin, has shown that oils boiling as 
low as 137° C may be obtained from a supposedly high-boiling (295° to 320° C) fraction of coal-tar creosote. 
These oils, although small in amount, were in all probability a mixture of xylenes and other of the higher 
homologues. 
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