E. J, Russell and E. H. Richards 545 



oxidation hypothesis fitted the facts better, the ammonia being supposed 

 to be oxidised direct to nitrogen, and not to form nitrate at all. This 

 view was commonly adopted in Germany i, and it received some support 

 by the announcement in 1897 that Wood and Wilcox^ had isolated 

 from bran infusions an organism able to liberate nitrogen direct from 

 nitrogenous compounds: so far as we know, however, this has not 

 been confirmed. 



On the other hand, Miintz and Laine^ working on sewage purification, 

 and dealing with percolation filters, reject the oxidation hypothesis. 

 In the first instance they note that loss only occurs in presence of organic 

 matter : it is not seen when a solution of ammonium salts is run on to 

 the filter. Secondly, they find that the addition of nitrate to the liquor 

 increases the loss of nitrogen. Laboratory experiments showed that 

 it caused an evolution of nitrogen, and by working in a vacuum a com- 

 plete balance was made as follows : 



But they found dissolved in the liquid: 



Free nitrogen 38-1 c.c. at n.t.p. = 23-9 mgms. 



which thus exactly balances the loss. 



This experiment shows that denitrification can take place and cause 

 loss of nitrogen, though it does not necessarily exclude the hypothesis 

 of a direct oxidation of ammonia. 



Sjollema and de Wildt, in the investigations referred to on p. 534. 

 also support this alternate nitrification and denitrification view on 

 the grounds that : 



1. Loss only occurs under aerobic conditions, and it is only under 

 these conditions that nitrate is formed. 



2. No loss occurs, even under aerobic conditions, if the temperature 

 reaches 50° C, the thermal death point of the nitrifying organisms. 



1 Thus Rumker, Mitt. Landw. Instit. Breslau, 1909, 4, 853-872, "Zur Frage der Stall- 

 mistzersetzung," directs attention to the great amount of nitrification that would be 

 required if the whole of the nitrogen were lost by alternate nitrification and denitrification, 

 and asks where the hme is to come from, apparently overlooking the fact that only a small 

 amount is necessary as it could be used over and over again. 



2 Journ. Soc. Chem. hid. 1897, 16, 510. 



* Annales Instit. Agron. 1911, 10. 2nd series, 1-48. 



