CHAPTER n. 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 solubiHty 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 ahphatic 

 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 fittle value. One might place the 

 flash point at not less than 70° or 75° C, 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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