The first of these is the pyridine series, including pyridine, C{5}H{5}N, picoline (methyl-pyridine), C{5}H{4}N(CH{3}), lutidine (dimethyl-pyridine), C{5}H{5}N(CH{3}){2}, and collidine (trimethyl-pyridine), C{5}H{2}N(CH{3}){3}.

When nicotine vapor is passed through a red-hot tube, it yields essentially collidine, and, with this, some pyridine, picoline, lutidine, and gases such as hydrogen, marsh-gas, and ethylene.

When distilled with potassium hydrate it yields quinoline, lutidine, and two isomeric collidines.

Pyridine, picoline, lutidine, and collidine, the first four members of the pyridine series, have, moreover, all been formed synthetically, although the processes are not such as would yield the products as cheaply as they can be gotten from Dippel's oil.