1820.J Physical Science during the Year 1819. 83 



be found in the second phial. Eight ounces of alcohol will 

 yield three ounces of nitric ether. (Jour, de Pharm. v. 433.) 



3. Naphtha. — From the experiments which I have related in 

 the Annals of Philosophy, xv. 307, compared with those of De 

 Saussure, on the naphtha of Amiano, there is reason I think to 

 conclude that the naphtha obtained artificially from coal by 

 repeated distillations is precisely similar in its properties to the 

 naphtha which rises spontaneously from the earth in Persia and 

 other parts of the world, supposing both to be brought to the 

 greatest possible state of purity. The following table exhibits 

 the specific gravity of the different specimens of naphtha both 

 artificial and natural which I have had an opportunity of 

 examining. 



Sp. Gr. at 60'. 



Pit coal naphtha (rectified 13 times) 0'850 



Ditto perfectly colourless 0'817 



Persian naphtha not rectified 0-753 



Naphtha of" Amiano rectified 0"758 



Naphtha, according to my trials, begins to boil at 320°, and it 

 may be heated up to the temperature of 352° ; so that its boiling 

 point is about five degrees higher than that of oil of turpentine. 



I found the specific gravity of the vapour of naphtha 2'263 at 

 the temperature of about 55°. Saussure, who made his experi- 

 ments at the temperature of 72"5°, found the specific gravity 

 2*833. I do not know whether to ascribe this difference to 

 errors in our experiments, or whether it is not rather owing to 

 the specific gravity increasing with the temperature, as happens 

 to a great extent with the vapour of water and of alcohol, sup- 

 posing these vapours in contact with the liquid from which they 

 were evolved. 



By analyzing naphtha by means of peroxide of copper, I 

 found it composed of 



13 atoms carbon = 9-75 



14 atoms hydrogen = 1*75 



11-50 

 So that an integrant particle of it weighs 11-5. 



3. Olive Oil. — Dr. Clarke has related an interesting observa- 

 tion respecting the regular crystallization of olive oil. A phial 

 of this oil having been left in a temperature of 35° exhibited a ' 

 number of white opaque prismatic radii rising from the bottom 

 of the vessel, and beautifully diverging in the transparent fluid. 

 When examined with a glass, these crystals were found to have 

 the form of mesotype ; that is to say, they were rectangular 

 prisms with square bases. (See Annals of Philosophy, xv. 329.) 



4. Pit Coal. — ^The different varieties of pit coal known and 

 employed for Great Britain for various purposes have hitherto 

 been very much overlooked by chemists ; I conceive, therefore, 



'f2 



