60 QUEENSLAND AGRICULTURAL JOURNAL. [1 Jan., 1898. 
Chemistry. 
DENITRIFICATION OR NITROGEN-WASTE. 
By J. C, BRUNNICH, 
Agricultural Chemist. 
THE great importance of the chemical element “nitrogen” as a constituent of 
certain animal and vegetable substances has been known for a long time, but 
only in recent years were valuable discoveries with regard to its share in the 
chemistry of vegetation made. We have hardly learned how the nitrogen of 
our atmosphere is assimilated by leguminous plants with the help of certain 
bacteria living in the root nodules of these plants, and learned how even to 
harness these bacteria into the service of agriculture, by cultivating them in 
laboratories and applying these pure cultures (“nitragin”) to the land, when 
we are startled with a new discovery that other bacteria, chiefly found in the 
dung of our barnyard manure, are capable of destroying or denitrifying 
nitrogenous compounds under liberation of free nitrogen, and thereby causing 
an enormous waste of this valuable element. Experiments are now being 
carried on by the celebrated agricultural chemists —W agner, of Darmstadt ; and 
Maercker, of Halle. The investigations are not as yet completed, but a few of 
the really startling results already obtained have been made known, and are 
discussed in an article in the Journal of the Royal Agricultural Society of 
England (No, 31, vol. 8, part 3). 
Before going into the details of these experiments, and in order to 
understand their full value, it will interest some of our readers to get some 
ideas about nitrogen and its compounds in general, its sources, and the manner 
in which it finds its way to the plants. 
The gas nitrogen, in its uncombined state, forms nearly four-fifths of the 
volume of our atmosphere. The atmosphere contains also small amounts of 
nitrogen in combination in the form of ammonia, nitrous and nitric acids. In 
nature, nitrogen is also found in the form of saltpetre, as nitrate of potash 
and nitrate of soda. 
In plants nitrogen is always present, though only in small quantities 
(about 1 per cent. in a crop of wheat and about 2 per cent. in a crop of clover); 
still it forms part of the most essential constituents, and is generally found in 
larger quantities in the seeds. Nitrogen, with a little sulphur and with the, 
in organic compounds ever-present elements—carbon, oxygen, and hydrogen, 
forms the albuminoids often called flesh-formers. To these albuminoids belong 
the fibrin found in the gluten of flour, the legumin or vegetable casein found in 
the seeds of beans, peas, &c., and the vegetable albumen found in the juice of 
most plants. All these compounds are closely related to the well-known 
albumen, or white of egg. Other nitrogen compounds found in plants are 
the nitrates, amides, and alkaloids (as quinine, theine, strychnine, &c.). 
Nitrogen is also an important constituent of the animal body ; the body of 
an ox contains, for instance, about 8 per cent. of nitrogen. The nitrogenous 
substances of the animal body are—Proteids (for instance, albumen or 
white of egg, which is coagulated by heat and is dissolved by the 
pepsin contained in the gastric juice of the stomach and converted into 
peptone) ; albuminoids (for instance, casein, the chief constituent of the 
curd of milk, and gelatine, a constituent of bones, skin, and sinews); and 
horny matter, as keratin, found in horns, nails, feathers, wool. In the brain 
and other nervous substances the chief constituent, lecithin, contains nitrogen 
as well as phosphorus. 
