EXPERIMENT STATION BULLETINS. 363 



THE SOLVENT ACTION OF SOIL BACTERIA UPON THE IN- 

 SOLUBLE PHOSPHATES OF RAW BONE MEAL AND 

 NATURAL RAW ROCK PHOSPHATE. 



DY WALTER G. SACKETT^ ANDREW J. PATTEN^ CHARLES W. BROWN, 



Special Bulletin No. 43. 



Of the many complicated questions which have claimed the almost 

 undivided attention of the soil chemist and the soil bacteriologist during 

 the past twenty-five years, the relation of microorganisms to the nitro- 

 gen of the soil stands paramount. Why this element should have received 

 more than its share of consideration is without doubt due to the fact 

 that it has been looked upon as of more importance than other plant 

 foods, not only because of the recognized dependence of the plant king- 

 dom, but also because of its greater money value and the limited supply 

 which at present seems to be a matter of no little concern. Our better 

 understanding of ammouification, nitrification, denitrification, nitrogen 

 assimilation and fixation, together with the scientific explanation of the 

 processes involved in these changes, stand out as witnesses to the ex- 

 cellent work of investigators who have given their entire time to con- 

 centrated research along these special lines. 



Within ver}' recent years, a second plant food element has demanded 

 recognition of the soil biologist, namely, phosphoric acid, 



xVccording to Wiley,* phosphorus exists in the soil in four forms: — 

 "1. Phosphoric acid in phosphates. 



2. Phosphoric acid in compound ethers similar to phosphoglycerates 

 which dilute acids and alkalies decompose slowly with regeneration of 

 phosphoric acid. 



3. Mineral compounds of phosphorus of the order of phosphites 

 which are resolved by oxidizing solutions like nitric acid with forma- 

 tion of phosphoric acid but Avhich are only oxidized to this stage by the 

 reagents employed after contact of indefinite length and uncertainty. 



4. In the case of organic compounds of the order of the oxide of 

 triethylphosphine, phosphorated phenyl compounds and cerebric acid 

 with extreme difliculty by the usual reagents employed in the wet way.'' 



''The mineral deposits of phosphorus as well as bone, are chiefly tri- 

 calcium phosphate while the slag compound resulting from the basic 

 treatment of iron ores rich in phospliorus is a tetra-calcium salt." 



Again in the natural, raw rock phosphate, we find calcium, iron and 

 aluminum combined with the phosphorus in the form of double salts. 



It is with such compounds as the two last mentioned which are only 



♦Principles and Practice of Agricultural Analysis, Wiley, Vol. I, p. 460. 



