XX.] ON THE THEORY OF NITRIFICATION. 473 



sociation for the Advancement of Science for 1850, on the Detection 

 of Nitrites and Nitrates, in which he indicated a delicate test for 

 these salts, showed the frequent presence of nitrites in rain-water, 

 and moreover pointed out that while nitrates are readily reduced to 

 nitrites in solution, these, "by oxidation, pass as readily into nitrates. 



