486 



AUGUSTO BONAZZI 



Experiment 227-a 



The apparatus used were made up according to figure 2. 



Aeration was carried on for about one hour and the complete 

 absence of CO2 ascertained by means of the barium hydroxide 

 bulb. The medium used was ignited and sterilized compost, 

 moistened with sterile Omeliansky solution in the proportion 

 of 40 cc. for each 100 gram of soil. One gram of basic MgCOs 

 had been placed in each flask, while dry, before sterilization. 



a, Concentrated NaOH; h, soda lime; c, soda lime; d, paraffin oil seal; e, culture 

 chamber with culture in — m;/, crucible with appropriate solution; g, Ba(0H)2 

 guard for detecting CO2; h, paraffin seals. 



All flasks were inoculated with a soil suspension which contained 

 negligible amounts of nitric or nitrous nitrogen. After inocula- 

 tion, the cotton plugs were removed, the flasks placed under the 

 bell jars, the seal made by pouring melted paraffin at the contact 

 of jar and plate and aeration started. The arrangement of the 

 flasks was the following: 



No. 1. Check uninoculated. 



No. 2. Air in system freed only of the initial CO2. 



No. 3. Air freed of CO2 throughout, containing NaOH 50 

 per cent. 



No. 4. Air containing only the CO2 developing from the 

 reaction of 5 mgm. Na2C03 and an excess of H2SO4 taking place 

 in/. 



