THE VALUE OF BONE MEAL 47 



animal origin, by the carbonic acid in water and by the humic 

 acids of the soil. The solutions thus produced are carried into 

 the soil where a complex series of actions due to unstable chem- 

 ical equilibria takes place. The phosphoric acid which in the 

 bones is combined with lime as tricalcium phosphate, and which in 

 solution is in the form of free acid or as monocalcium phosphate, 

 tends again to form more stable compounds and is finally deposited 

 chiefly in the form in which it existed in the bones, viz., trical- 

 cium phosphate. All these changes take place strictly in harmony 

 with the laws of physical chemistry. The deposits of phosphates, 

 therefore, are due to chemical rather than geological phenomena. 



54. The Value of Bone Meal from which the Nitrogen Constit- 

 uents Have Been Extracted, as a Fertilizing Reagent. When 

 fresh, finely ground bones are applied to use as a fertilizer and 

 valuable results are obtained they may be ascribed either to the 

 nitrogen constituent in bone or to its content of phosphoric acid. 

 In general, the bone phosphate has not been regarded as being 

 of great value, and the chief utility of ground bone has been 

 ascribed to its nitrogen constituent. If the value of a phosphate 

 as a fertilizer be governed by its solubility in ammonium citrate 

 or citric acid, it has been shown that considerable portions of 

 phosphoric acid in finely ground bone are soluble in these re- 

 agents. 



Since the original observations of Huston have shown that the 

 phosphoric acid of finely ground bone is soluble in ammonium 

 citrate, this problem has been studied by many other observers. 

 Reitmair has made investigations on this subject with the results 

 which follow. 25 The observations were carried on at the same 

 time with degelatinized bone meal and basic slags, and the quan- 

 tity of rye produced per hectare when these bodies were used 

 for the fertilizing reagents was determined. As a result 

 of these investigations Reitmair concluded that the solu- 

 bility of a phosphate in citric acid is no criterion for its value as 

 a fertilizer or as a measure of its solubility in the soil. The solu- 

 bility in citric acid of phosphate is no measure for the quantities 

 of the active forms of phosphoric acid which are given. It is 

 15 Wiener landwirtschaftliche Zeitung, 1905, 55 : 879-881 and 889-891. 



