248 Scientific Proceedings, Royal Dublin Society. 
liquid in which it was immersed, and that the decomposition is 
analogous in character to that which Gayon and Dupetit! have 
shown nitre undergoes, when it is present in the nutrient medium > 
in which certain organisms are grown. 
Those observers isolated from sewage two aerobic organisms, 
which they named Bacterium denitrificans a and 3. By quanti- 
tative experiments, they showed that, when these organisms are 
grown in almost any infusion containing organic matter and also 
nitre, the whole of the nitrogen of the nitre is evolved as gas, and 
that the whole of its available oxygen is combined with carbon to 
form carbon dioxide. Some ammonia is formed, but it is derived, 
they state, from the nitrogenous constituents of the nutrient 
medium employed. 
The authors show that the organisms will not develop in 
liquids free from nitrate and kept out of contact with air. They 
therefore regard the decomposition of the nitrate as a fermentation 
consisting of the direct oxidation of organic carbon at the expense 
of its available oxygen. 
The decomposition of the nitrate may therefore be expressed 
thus :— 
qi): 4 KNO, = 2N, + 2K,0 + 5 O,. 
Qh “sce 0) = sicor 
(3). 2 K,0 + 2 CO, = 2 K.COs. 
If the decomposition of the peroxide above described be 
regarded as analogous in character, then the whole of its available 
oxygen should combine with organic carbon, and manganous 
carbonate be finally formed, thus :—- 
(1). 2 MnO, = 2 MnO + O,. 
(2). C40, = CO, 
(3). MnO+CO, = MnCO,. 
That these reactions would be attended with the evolution of a 
1 Ann. de la Science Agronomique, 1885, I., 226; also abstract Chem. Soc. Journ., 
XLIX., p. 820. 
