128 Dr Gregory on the Composition of 



The naphtha examined by Saussure, then, that analyzed by 

 Dr Thomson, that which may be extracted from the Rangoon 

 petroleum, and that now sold in Paris, all agree in yielding a li- 

 quid of sp. gr. 0.753 to .765 ; while that of oil of turpentine is 

 0.830, and has never been stated lower than 790. Moreover, Dr 

 Thomson's Persian naphtha, that of Rangoon, and the commer- 

 cial naphtha from Paris, all possess, in a considerable degree, the 

 characteristic odour of eupione. If we consider that the specific 

 gravity of pure eupione is 655, we shall not be surprised that its 

 odour is somewhat disguised, when it is so impure as to have the 

 sp. gr. 750. But we have other means of distinguishing between 

 eupione and oil of turpentine. The first is the action of nitric 

 acid. The violent decomposition produced by it in oil of tur- 

 pentine is well known. I have tried Persian, Rangoon, and com- 

 mercial naphtha with the very strongest fuming nitric acid, such 

 as set fire to turpentine, but there was no action except at a high 

 temperature, when a brown colour was produced. In fact, the 

 Rangoon naphtha, during its purification, was distilled with sul- 

 phuric acid and nitre without change. The next test was the 

 action of iodine, which produces a slight explosion when intro- 

 duced into oil of turpentine. In the three varieties of naphtha 

 just mentioned, there was scarcely any action beyond simple so- 

 lution, and, in all, the solution had a rich violet colour, which is 

 the colour of a solution of iodine in eupione. I am induced to 

 suspect that a small quantity of oil of turpentine may be present, 

 from the slight action manifested by nitric acid, and even by 

 iodine, at a high temperature. But the presence of oil of tur- 

 pentine is to be looked for in these liquids, if we consider them 

 the products of the destructive distillation of Coniferee, since the 

 first effect of heat would be to expel the oil of turpentine, which 

 would afterwards mix with the products of the true destructive 

 distillation. Even admitting, therefore, that these varieties of 

 naphtha contain oil of turpentine, still I conceive we must be sa- 

 tisfied that it is not a chief ingredient, far less, as in the oils ex- 



