CHAPTER H. PHYSICAL PROPERTIES OF COAL-TAR CREOSOTES. 
SOLUBILITY. 
The solubility of creosote in some solvents may be considered as 
a physical property; in other solvents a chemical reaction is involved. 
Usually, coal-tar creosote is completely soluble in chloroform, carbon 
tetrachloride, carbon bisulphide, ether, and absolute alcohol, although 
the individual constituents that go to make up the creosotes are 
frequently not soluble in some of these solvents. The influence of 
soluble constituents in increasing the solubility of those that usually 
are not soluble in the oil is well known to chemists. As an instance 
of this, it may be cited that, in the purification of anthracene from 
a mixture of phenanthrene and anthracene, the original material is 
quite soluble in warm 95 per cent alcohol. On cooling, a considerable 
amount of very impure anthracene crystallizes. A greater amount 
of alcohol is now required to dissolve this anthracene than was 
required to dissolve the original material, although it has been 
reduced to a smaller amount. Each time the crystallization is 
effected, the material becomes somewhat purer, and finally the 
anthracene is scarcely soluble in absolute alcohol. All aromatic 
hydrocarbons are soluble in dimethyl sulphate, but the aliphatic 
hydrocarbons are not soluble in it. As a rule, therefore, coal-tar 
creosote is completely soluble in this reagent; but, if paraffin com- 
pounds are present, it can not be expected that they would be sepa- 
rated quantitatively by the use of this solvent alone. 
COLOR AND ODOR. 
The color of coal-tar creosote is usually a deep yellow to a dark 
brown, depending somewhat upon its age. When first distilled, it 
is a clear yellow oil with a greenish cast, which rapidly changes 
to brown on contact with the air. The odor is rather difficult to 
describe. If naphthalene is present in considerable quantities, this 
odor predominates, but in general the odor can be described only 
as " tarry." 
FLASH AND BURNING POINTS. 
It is usual in stating the physical properties of oils to give some 
idea of their flash and burning points. The composition of creosote 
oil varies so greatly, however, that the determination of the flash 
and burning points is of very little value. One might place the 
flash point at not less than 70° or 75° O, and the oil may be expected 
to flash at 80° C. under almost any conditions. The burning point 
is between 90° and 100° C. 
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