Nitrification of Ammonia Adsorbed on Colloidal Clay

The conditions controlling nitrification in aqueous solutions have been studied very specifically. Less definite controls and less refinement in methods have obtained for studies of this process within the soil. The complexity of a sand, silt, and clay mixture as soil prohibits an accuracy great enough to encompass all the various chemical aspects of so delicate a microbiological performance as nitrification. . In the work reported here, the colloidal fraction of the soil was employed as a medium for study of this process in the belief that it would permit a more refined technique and yet give a close approach to the soil itself. This procedure eliminates the bulky, and almost chemically inactive, soil fraction in the form of the sand and silt, and locates the process in that portion of the soil where very probably its activities really occur. It escapes, also, the solution condition of the ions, but uses these in the case of the colloidal clay in the wholly adsorbed and almost un-ionized form even though the clay is in an aqueous suspension. .Experimental