The researches of Liebig (1823), Liebig and Gay-Lussac (1824), and of Liebig again in 1838 showed the acid to be isomeric with cyanic acid, and probably (Hcno) 2, since it gave mixed and acid salts.
By passing the vapour of this compound through a red-hot tube, it yields the isomeric a0- pyridylpyrrol, the potassium salt of which with methyl iodide gives a substance methylated both in the pyridine and pyrrol nuclei.
The principal elements are found in various combinations, the hydrocarbons of the Pennsylvania oils being mainly paraffins (q.v.), while those of Caucasian petroleum belong for the most part to the naphthenes, isomeric with the olefines (q.v.).
These three hydrocarbons are isomeric, i.e.
Starting with the three isomeric compounds, he found that one gave two tribrombenzenes, another gave three, while the third gave only one.