This series is also found in relatively larger proportion in what is known as Dippel's oil, the product of the dry distillation of bones.

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.

DIPPEL, JOHANN KONRAD, a celebrated German alchemist; professed to have discovered the philosopher's stone; did discover Prussian blue, and an animal oil that bears his name (1672-1734).

DIPPEL'S OIL, an oil obtained from the distinctive distillation of horn bones.