48 AGRICULTURAL ANALYSIS 



not even a measure, as has often been supposed, of the favorable 

 mechanic properties of phosphatic manure. The larger particles 

 of bone phosphate and of basic slags were brought into solution 

 both by the usual and by the modified digestion methods prac- 

 ticed. Various samples of the bone meal from different sources 

 were treated with citric acid, according to the usual method, to 

 determine the percentage of solubility therein, and the quantity 

 of fine particles, passed through a sieve with fine mesh, was de- 

 termined. A bone meal containing 86.5 per cent, of fine particles 

 showed a solubility of 92.3 per cent, in citric acid, while the de- 

 gelatinized sample of bone meal containing only 12.6 per cent, of 

 fine particles showed a solubility of 87.6 per cent. Thus, while 

 it is generally true that the solubility in citric acid varies inversely 

 with the size of the particles, it does not vary proportionately 

 thereto. The period of digestion in each case was one-half hour. 



It is evident from the above that the agricultural chemist has 

 yet much to learn concerning the character and speed of the solu- 

 tion of phosphate in a soil. The changes which take place in the 

 ordinary digestion in citric acid in the laboratory are evidently 

 of a very different degree of magnitude and are carried on with 

 a very different degree of speed from that which takes place dur- 

 ing the growing period in the soil itself. 



All the experiments conducted by Reitmair indicate that the 

 degelatinized phosphoric acid has a distinct value as a phosphatic 

 fertilizer and this depends primarily upon the state of subdivision 

 and is indicated only approximately by its solubility in citric acid. 

 Attention, however, must be called to the fact that in the manu- 

 facture of degelatinized bone meal it has not yet been possible to 

 produce a product entirely free from nitrogen on a commercial 

 scale. The last traces of nitrogen are not removed and 

 there usually remains in the degelatinized bone about 

 0.5 per cent, of nitrogen. This residue must be re- 

 garded as an unavoidable contamination of the bone 

 meal for experimental purposes, but it is of a magnitude so 

 small as to be practically ignored in the experimental work. It is 

 evident, therefore, that any attempt to determine the fertilizing 

 value either of degelatinized bone or of basic slag by its solubility 



