SOME ASPECTS OF NITRATE REDUCTION 



iment in which the gas production was determined in three identical 

 cultures of Denitrobacillus licheniformis in which the partial pressure of 

 nitrous oxide in the gas phase was varied. In one culture the gas could 

 escape at normal atmospheric pressure, in the second one the partial 

 pressure was reduced at regular intervals by evacuation, whilst in the 

 third case the culture was brought in a thick-walled sealed tube, 

 under such conditions that the final pressure of the gas surpassed 10 

 atmospheres. The influence of the various measures on the composi- 

 tion of the gas evolved is shown in Table I ; the figures given leave 



The influence of the partial pressure of nitrous oxide on the 



composition of the gas evolved in a denitrification experiment 



with Denitrobacillus licheniformis 



Gas evolved in ml Composition gas in % 



N 2 N 2 N 2 N 2 



Vacuum 16 32 33,3 66,7 



1 Atmosphere 42 8 84,0 16,0 



Pressure 52 1 98,2 1,8 



no doubt that with increasing partial pressure of the nitrous oxide in 

 the gas atmosphere this gas is to a larger extent converted into ni- 

 trogen. 



nitric acid HNO3 

 2H^j 



I 

 • ,s add HNOo 



2H-J 



nitrous 

 I oxide 



itroxyi HNO -» V 2 H 2 N 2 2 -^ 1 /2N 2 0+ 1 /2H 2 



2H- 



H i r 



H 



hydroxyzine H,NOH ' -^V2 N 2 



nitrogen 





, 



491 



