NITRIFICATION 791 



also by good tillage and drainage so as to provide a suitable and 

 thorough supply of air. 



The nitrifying bacteria are remarkable in being organisms 

 which can build up the protoplasm and other constituents 

 of their bodies entirely from inorganic compounds even in 

 the dark. 



The carbon essential for their nutrition is derived from 

 the carbon dioxide of the air or from bicarbonates, not from 

 neutral carbonates, for the organisms refuse to develop in 

 solutions containing the latter compounds unless free carbon 

 dioxide is present also. Instead of utilising the energy of 

 the sun's rays to enable them to dissociate the carbon dioxide, 

 as is the case with green plants, they obtain the energy necessary 

 for the work from the oxidation of ammonium compounds 

 and nitrites. 



It is thus seen that the nitrification prdcess which is of 

 such beneficial importance to the human race is not mere 

 gratuitous philanthropy on the part of the bacteria, but is 

 carried on by the latter for the maintenance of their own 

 existence. 



Ex. 328. — Make up a solution as follows : — 



Water, . . . . ,1 Litre. 



Ammonium Chloride, . . . 'oS Gram. 



Potassium Phosphate, . . . '04 ,, 



Magnesium Sulphate, . . . "02 „ 



Calcium Carbonate, . . . "05 ,, 



Sodium Potassium Tartrate, . . '08 ,, 



Place 100 c. c. of the solution in small glass £asks and add about '1 gram 

 of ordinary arable soil to each. After plugging the mouth of each flask with 

 cotton-wool place them in a dark cupboard in a warm room. 



Withdraw S c.c. from each flask every three or four days and test half of 

 each S c.c. : — (l) for ammonia with Nessler's solution ; {2) for nitrites or 

 nitrates, by adding first a drop of diphenylamine sulphate in sulphuric acid 

 and then two or three c.c. of strong sulphuric acid : the development of a 

 violet-blue colour shows the presence of nitrites or nitrates. 



