30 LABOEATOEY BACTEEIOLOGY. 



12. At the end of two weeks determine, by the phenol- 

 sulfonic acid method the nitrates present in samples- 1, 2, 

 5, 6, 9, 10, 13 and 14; filtering the solutions and leaching 

 the soil after additions of a little lime, making up to con- 

 venient volumes and aliquoting in the usual way. 



13. At the end of four weeks the nitrates present in the 

 remaining samples are determined similarly. 



14. Calculate the per cent, of ammonia nitrogen nitrified 

 in the soils and in the solutions, in the same length of time, 

 in the presence or absence of lime, and compare the rate of 

 oxidation under these conditions. 



