Note 104 — Chapter IV · NITRIFICATION.
Reading edition
Pasteur had already in 1862 expressed the opinion that nitrification might probably be in some way connected with ferments. A. Müller (see 'Journal of Chemical Society,' 1879, p. 249) was the first to advance the opinion that nitrification was due to the action of a ferment. This conclusion he was led to by the observation that while the ammonia in sewage was converted into nitric acid, no change took place in solutions of ammonia or urine prepared in the laboratory.