"6 Dr. Mac CuLLOCH o« certain products 



softest specimens of the pitch are nearly as soluble, leaving only 

 a small residuum, which is infusible and powdery. The harder 

 Specimens become in proportion less soluble, and leave a larger 

 residuum ; and those which have been the longest exposed to heat 

 scarcely give a stain to the alcohol, resembling in this respect the 

 driest specimens of asphaltum. The analogy is here very apparent, 

 for asphaltum may approach more or less to petroleum, and the 

 various specimens of it are found to exhibit various degrees of 

 solubility in alcohol. That which is least fusible in the fire, is, in 

 both cases, the least soluble in alcohol. And by this consideration, 

 the jarring accounts which have been given of the solubility of as- 

 phaltum in alcohol may be reconciled, and it will be seen in the sequel, 

 that the history of this substance illustrates, in every respect, the true 

 nature of the several varieties of the bitumens, substances whose 

 mutual relations, and the causes of whose chemical diversity have 

 hitherto not been understood. 



If a perfectly soluble specimen be dissolved in alcohol, it is ob- 

 tained unchanged by evaporating the spirit. In any other case, the 

 matter which the alcohol has taken up is precisely similar to the 

 pitch in its first state, and the residuum resembles that which is the 

 result of fusion when it refuses longer to melt. Alcohol therefore 

 separates the pure pitch from that, which by a process of decom- 

 position has been nearly carbonized. Ether acts upon this sub- 

 stance as readily and in the same manner as alcohol does. In 

 lixivium of pure potash it is more completely soluble than in alcohol, 

 and forms with it an intensely brown solution which is diffusible in 

 water without change, and which, on the addition of an acid, 

 deposits the matter in a powdery form and apparently unchanged. 

 It is also soluble in water of ammonia with similar appearances. 

 It is scarcely soluble in the pale oil of turpentine, but more readily 



