648 



PRINCIPLES OF SOIL MICROBIOLOGY 



bacteria and the amount of bases brought into solution from the mineral, 

 since the magnitude of the effect of bacterial end-products upon a 

 mineral depends upon the equilibrium established. 13 It was suggested 

 that the action of bacterial end-products, acid in nature, upon minerals 

 is explainable as a chemical reaction. Figures 48 and 49 show the 

 action of mineral acids and bacterial cultures upon some typical sili- 



4.0 



5.0 



logCh 4.0 



3.0 



Fig. 49. Influence of B. lactis acidi upon the solubility of orthoclase (from 

 Wright). 



cates. The numbers along the ordinates represent the logarithms of 

 the hydrogen-ion concentration, or log Ch. Those along the abscissae 

 measure the logarithm of the concentrations, or log of Ca, of Mg, of 

 Fe or K. 



is Wright, D. Equilibrium studies with certain acids and minerals and their 

 probable relation to the decomposition of minerals by bacteria. Univ. Cal. 

 Publ. Agr. Sci., 4: 247-337. 1922. 



