SOIL BACTERIA.: 



The question then is How is the ammonia converted into nitric 

 acid? it was not till 1877 that two French chemists showed by a 

 very simple experiment that the power of soils to convert nitrogen, 

 that is, the ammonia of the manure, into nitric acid was the work of 

 some kind of living thing or organism. 



Muntz and Schloessing* allowed dilute sewage to trickle down 

 through a vessel packed with chalk, i.e., carbonate of lime. They 

 found that no change took place for the first fortnight or three weeks, 

 but then suddenly the fluid that accumulated at the bottom of the vesse] 

 was found to contain nitrate of lime, i.e., nitric acid had been formed. 

 If this process of nitrification was due to some chemical or physical 

 procedure it should set in at once. Why then was this delay ? 

 They argued that it could only be because the process was biological ; 

 that is, was due to some living organism, and the period of delay was 

 needed for the multiplication of this organism. 



The theory was tested by adding chloroform to the soil. This, of 

 course, would put a stop to the action of any organisms. The pro- 

 cess at once ceased. -But on the replacement of the chloroform by 

 air or oxygen the process set in again. That is, the organisms had 

 been temporarily numbed, but had recovered in the air. Although 

 Muntz did not follow this particular aspect of the matter any further, 

 others did, and there, arose a new branch of science, that of "Soil 

 Bacteriology." 



Amongst those who continued to work at this problem was notably 

 Warington, who worked many years at Rothamsted. After a series 

 of experiments he obtained a culture which was able to turn 

 the ammonia into nitrous acid. This was in 1879. But he recog- 

 nised that he must go further, for nitrous acid only combines to form 

 nitrites, which are quite useless to plants. After two more years 

 of work he obtained a further culture which was able to convert the 

 nitrous acid into nitric acid. This was an important step, and 

 perhaps you might think that it sufficed. So perhaps it would for 

 the practical man, but the scientific man wants to know how these 

 two changes are brought about. What is there in the liquids that 

 bring about these chemical changes ? Muntz had proved that some 

 organism was concerned in the process, and people now set about to 

 try and find what that organism might be. The credit of discover- 

 ing a specific organism in these cultures is due to Dr. Percy 

 Frankland, of the Royal College of Science in London. t He in 1890 

 succeeded in isolating a special bacterium, and his discovery 



JDr. Russell's useful work, "Soil Conditions and Plant Growth" (Longmans, 

 Green, and Co., 1917), contains an admirable historical account of all that 

 relates to the soil. 



*Schloessing and Muntz, "Sur la nitrification par les ferments organises " 

 Comptes Rendues. 1877. 

 tFrankland, loc cit, p. 87. 



